# Seminar 14: Pelvic Masses and Ovarian Disease

## OB/GYN Clerkship

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## Learning Objectives

By the end of this seminar, students will be able to:

1. Construct a differential diagnosis for pelvic masses organized by organ of origin and patient age group
2. Describe the pathophysiology, imaging characteristics, and natural history of functional ovarian cysts
3. Differentiate benign ovarian neoplasms including mature teratoma, serous cystadenoma, mucinous cystadenoma, and fibroma based on clinical and imaging features
4. Classify malignant ovarian neoplasms by cell type and apply tumor markers to guide evaluation and management
5. Evaluate adnexal masses using ultrasound characteristics, risk stratification tools, and referral criteria for gynecologic oncology
6. Recognize ovarian torsion as a surgical emergency and apply management principles for ovarian cysts across age groups

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## Seminar Outline

### Section 1: Approach to Pelvic Mass

The differential diagnosis of a pelvic mass encompasses structures from multiple organ systems within the pelvis, and a systematic approach to the origin of the mass is essential for efficient evaluation. Ovarian masses include functional cysts, benign neoplasms, and malignant tumors, representing the most common gynecologic pelvic masses in reproductive-age women. Uterine masses include leiomyomas, which are the most common pelvic tumors overall, and adenomyosis. Tubal masses include ectopic pregnancy, hydrosalpinx, and tubo-ovarian abscess. Non-gynecologic structures must also be considered, including gastrointestinal masses such as appendicitis, diverticulitis, and colon cancer, and urinary tract masses including a distended bladder and pelvic kidney. A thorough history and physical examination combined with targeted imaging can usually identify the organ of origin and narrow the differential.

The age of the patient significantly influences the differential diagnosis of a pelvic mass and guides the urgency of evaluation. In pediatric and adolescent patients, functional cysts are common, but germ cell tumors must be considered, as they represent the most common malignant ovarian neoplasm in this age group. Reproductive-age women most commonly present with functional cysts, endometriomas, and mature cystic teratomas, with epithelial ovarian cancer being uncommon but not impossible. Postmenopausal women require a heightened level of suspicion for malignancy, as the absence of ovulatory function makes functional cysts less likely, and any persistent ovarian mass in this population carries a higher risk of neoplasia. The clinical approach should always consider age as a primary factor in determining the pretest probability of malignancy.

The history and physical examination provide critical information that guides the diagnostic workup. Historical features to assess include the onset and character of pain, menstrual changes, gastrointestinal and genitourinary symptoms, weight loss or constitutional symptoms, and family history of ovarian, breast, or colon cancer. Physical examination findings include the location, size, and tenderness of the mass, its mobility or fixation to surrounding structures, the presence of ascites detected by shifting dullness, and nodularity in the cul-de-sac that may suggest malignancy or endometriosis. The combination of historical and physical findings creates a clinical picture that informs the selection and interpretation of imaging studies.

Imaging is the cornerstone of pelvic mass evaluation, with the modality selected based on the clinical scenario and the information needed. Transvaginal ultrasound is the first-line imaging study for all pelvic masses, providing excellent resolution of ovarian morphology, cyst characteristics, and blood flow patterns. Magnetic resonance imaging is used when ultrasound findings are indeterminate, as it offers superior tissue characterization and can distinguish fat, blood, and solid components with high accuracy. Computed tomography is preferred when malignancy is suspected, as it provides comprehensive evaluation for peritoneal disease, lymphadenopathy, and distant metastases for staging purposes. Positron emission tomography is reserved for staging of confirmed malignancy and detection of recurrent disease, and is not routinely used in the initial evaluation of pelvic masses.

<image>Panel A: Pelvic mass differential diagnosis organized by organ of origin showing ovarian (functional cysts, neoplasms), uterine (fibroids, adenomyosis), tubal (ectopic, hydrosalpinx, TOA), gastrointestinal (appendicitis, diverticulitis, colon cancer), and urinary (distended bladder, pelvic kidney). Panel B: Age-based differential showing pediatric and adolescent (functional cysts, germ cell tumors), reproductive age (functional cysts, endometriomas, dermoids), and postmenopausal (higher malignancy risk, epithelial cancer) with corresponding prevalence. Panel C: History and physical examination framework showing pain characteristics, menstrual changes, constitutional symptoms, family history, mass location and mobility, ascites, and cul-de-sac nodularity. Panel D: Imaging modality selection showing transvaginal ultrasound (first-line), MRI (indeterminate findings, tissue characterization), CT (suspected malignancy, staging), and PET (confirmed malignancy, recurrence).</image>

### Section 2: Functional Ovarian Cysts

Follicular cysts develop when a dominant follicle fails to rupture during ovulation and continues to enlarge under the influence of follicle-stimulating hormone. These cysts are typically less than 3 centimeters in diameter, though they may occasionally grow larger, and appear as simple, anechoic, thin-walled structures on ultrasound with posterior acoustic enhancement. Most follicular cysts are asymptomatic and are discovered incidentally during pelvic examination or imaging performed for other reasons. Management is expectant with observation, as the vast majority resolve spontaneously within 1 to 3 menstrual cycles without intervention. Oral contraceptive pills do not hasten resolution of existing follicular cysts but may prevent the formation of new functional cysts by suppressing ovulation.

Corpus luteum cysts form when the corpus luteum, the structure that develops after ovulation to produce progesterone, fills with blood and fails to regress normally. These cysts may grow up to 8 centimeters in diameter and have a characteristic complex appearance on ultrasound with a thick echogenic wall, internal echoes representing blood products, and circumferential vascularity described as the "ring of fire" on Doppler imaging. Patients may experience unilateral pelvic pain, and rupture of a corpus luteum cyst can produce acute pain and hemoperitoneum. Management is observation for stable patients, with monitoring for signs of hemodynamic instability. Surgical intervention with laparoscopy is indicated when rupture produces ongoing hemorrhage with hemodynamic compromise.

Hemorrhagic cysts result from bleeding into a follicle or corpus luteum, creating a characteristic ultrasound appearance that evolves over time. The acute hemorrhagic cyst demonstrates a "fishnet" or "cobweb" pattern of intracystic fibrin strands, which progressively organize and retract as the clot matures. The clinical presentation may be dramatic, with acute onset of unilateral pelvic pain mimicking ovarian torsion, ruptured ectopic pregnancy, or appendicitis. Most hemorrhagic cysts are managed supportively with analgesics and observation, as they typically resolve over 6 to 8 weeks. Surgical intervention is reserved for patients who are hemodynamically unstable due to significant intraperitoneal hemorrhage, or when the imaging appearance is atypical and a neoplastic process cannot be excluded.

Theca lutein cysts develop in response to elevated levels of human chorionic gonadotropin and are associated with conditions that produce markedly elevated hormone levels. These conditions include hydatidiform mole, multiple gestation, and ovarian hyperstimulation during fertility treatment. Theca lutein cysts are characteristically bilateral and multiloculated, with the ovaries often massively enlarged. The primary complication is ovarian torsion due to the increased size and weight of the stimulated ovaries. Management is expectant, as the cysts resolve spontaneously once human chorionic gonadotropin levels decline, whether through treatment of the underlying molar pregnancy, delivery of the gestation, or cessation of ovulation induction. Patients should be counseled to avoid vigorous physical activity to reduce the risk of torsion.

<image>Panel A: Follicular cyst ultrasound showing simple anechoic thin-walled structure less than 3 centimeters with posterior acoustic enhancement, expectant management algorithm, and resolution timeline of 1 to 3 cycles. Panel B: Corpus luteum cyst showing complex ultrasound appearance with thick echogenic wall, internal echoes, "ring of fire" Doppler vascularity, potential for rupture with hemoperitoneum, and management by observation versus surgery for hemodynamic instability. Panel C: Hemorrhagic cyst ultrasound evolution showing "fishnet" and "cobweb" fibrin strand patterns, progressive clot organization, differential diagnosis (torsion, ectopic, appendicitis), and 6 to 8 week resolution timeline. Panel D: Theca lutein cysts showing bilateral multiloculated appearance, association with elevated hCG (molar pregnancy, multiples, ovulation induction), torsion risk, and spontaneous resolution with hCG decline.</image>

### Section 3: Benign Ovarian Neoplasms

The mature cystic teratoma, commonly known as a dermoid cyst, is the most common benign ovarian neoplasm in reproductive-age women and arises from germ cell differentiation. These tumors contain mature tissue derived from all three embryonic germ layers, including ectodermal elements such as hair, skin, and sebaceous material, mesodermal elements such as bone and cartilage, and endodermal elements such as thyroid tissue. On ultrasound, dermoids produce a characteristic appearance with an echogenic nodule known as a dermoid plug or Rokitansky protuberance, acoustic shadowing from calcified components, and a mixed echogenicity pattern. Approximately 10 to 15 percent are bilateral. The risk of malignant transformation is less than 1 percent and occurs primarily in postmenopausal women. Management includes ovarian cystectomy for symptomatic lesions or those exceeding 5 centimeters, and torsion is a significant risk due to the density and weight of the tumor.

Serous cystadenomas are benign epithelial ovarian tumors that present as thin-walled, unilocular cysts filled with clear serous fluid. These tumors may range from a few centimeters to quite large and are bilateral in approximately 20 percent of cases. The ultrasound appearance is that of a simple or near-simple cyst with thin, smooth walls and no solid components or papillary projections, making them difficult to distinguish from large functional cysts on imaging alone. Serous cystadenomas carry a small risk of being borderline or low malignant potential tumors, and definitive diagnosis requires histologic examination of the surgically removed specimen. Management options include ovarian cystectomy for women desiring fertility preservation or oophorectomy for postmenopausal women or those in whom malignancy cannot be excluded.

Mucinous cystadenomas are benign epithelial ovarian tumors characterized by multiloculated cysts filled with thick, mucinous fluid, and they can grow to enormous sizes, occasionally exceeding 30 centimeters in diameter. The multiloculated appearance with internal septations distinguishes mucinous cystadenomas from serous tumors on imaging. These tumors require careful surgical removal because rupture during surgery can lead to pseudomyxoma peritonei, a condition in which mucinous material implants throughout the peritoneal cavity and causes progressive abdominal distension. Intact removal of mucinous tumors is therefore essential, and spill should be avoided during cystectomy or oophorectomy. Like serous cystadenomas, definitive diagnosis requires histopathologic assessment to exclude borderline or malignant components.

Fibromas and fibrothecomas are sex cord-stromal tumors that present as solid, hypoechoic ovarian masses and account for approximately 4 percent of all ovarian tumors. These tumors are composed of spindle-shaped fibroblasts and may produce estrogen when thecal elements are present. The association of an ovarian fibroma with ascites and pleural effusion is known as Meigs syndrome, a benign condition that resolves completely after surgical removal of the tumor and must be distinguished from advanced ovarian malignancy with ascites and pleural metastases. Fibromas are characteristically solid on ultrasound with acoustic shadowing, and they may be difficult to distinguish from pedunculated subserosal fibroids or solid malignant ovarian tumors without MRI or surgical evaluation. Management is surgical removal, and prognosis is excellent as these tumors are virtually always benign.

<image>Panel A: Mature cystic teratoma (dermoid) showing ultrasound with echogenic dermoid plug, acoustic shadowing from calcifications, mixed echogenicity, contents including hair, teeth, and sebaceous material, 10 to 15 percent bilateral rate, and less than 1 percent malignant transformation risk. Panel B: Serous cystadenoma showing thin-walled unilocular cyst with clear serous fluid, smooth walls without solid components, 20 percent bilateral rate, and management by cystectomy versus oophorectomy. Panel C: Mucinous cystadenoma showing multiloculated cyst with internal septations, thick mucinous fluid, potential for massive size, pseudomyxoma peritonei risk with rupture, and intact removal requirement. Panel D: Fibroma and fibrothecoma showing solid hypoechoic mass, spindle-cell histology, Meigs syndrome triad (fibroma, ascites, pleural effusion), differentiation from malignancy, and complete resolution after surgical removal.</image>

### Section 4: Malignant Ovarian Neoplasms

Epithelial ovarian cancer accounts for approximately 90 percent of all ovarian malignancies and represents the leading cause of death from gynecologic cancer in the developed world. The subtypes include high-grade serous (the most common and aggressive), low-grade serous, endometrioid, clear cell, and mucinous carcinomas, each with distinct molecular profiles and clinical behaviors. High-grade serous carcinoma is now believed to originate from the fallopian tube epithelium rather than the ovarian surface and is typically diagnosed at an advanced stage due to the absence of early symptoms. CA-125 is elevated in approximately 80 percent of epithelial ovarian cancers but lacks specificity, as it is also elevated in endometriosis, pelvic inflammatory disease, cirrhosis, and early pregnancy. The typical presentation includes abdominal distension from ascites, early satiety, pelvic or abdominal pain, and urinary frequency, often described as vague and nonspecific symptoms that have been present for weeks to months.

Germ cell tumors are the most common malignant ovarian neoplasms in children, adolescents, and young women, and they are distinguished from epithelial cancers by their cell of origin, clinical behavior, and treatment response. Dysgerminoma is the most common malignant germ cell tumor, analogous to testicular seminoma, and is highly radiosensitive and chemosensitive with an excellent prognosis even in advanced stages. Immature teratoma contains immature or embryonal tissue in contrast to its benign counterpart, the mature teratoma, and is graded by the amount of immature neuroepithelium present. Yolk sac tumor, also known as endodermal sinus tumor, produces alpha-fetoprotein, which serves as both a diagnostic marker and a tool for monitoring treatment response. Choriocarcinoma produces beta-human chorionic gonadotropin and must be distinguished from gestational trophoblastic disease. Fertility-sparing surgery with unilateral salpingo-oophorectomy is the standard surgical approach for germ cell tumors in young women.

Sex cord-stromal tumors arise from the ovarian stroma and sex cord cells and represent approximately 5 to 8 percent of ovarian malignancies. Granulosa cell tumors are the most common sex cord-stromal neoplasm and characteristically produce estrogen, which may cause precocious puberty in prepubertal girls, irregular bleeding in reproductive-age women, and postmenopausal bleeding in older women. Inhibin serves as the primary tumor marker for granulosa cell tumors and is used for monitoring. Sertoli-Leydig cell tumors produce androgens and may present with virilization including hirsutism, deepening voice, and clitoromegaly. Sex cord-stromal tumors generally have a low malignant potential and favorable prognosis, though granulosa cell tumors are notable for their propensity for late recurrence, occurring years to decades after initial treatment, necessitating long-term surveillance.

Metastatic tumors to the ovary arise from primary cancers elsewhere in the body and must be considered in the differential diagnosis of ovarian masses. The Krukenberg tumor is a metastatic ovarian tumor, typically bilateral, composed of signet ring cells that most commonly originate from gastric cancer, though colon and breast primaries may also produce this pattern. Breast cancer is a common source of ovarian metastases and should be considered in patients with a personal history of breast malignancy who present with adnexal masses. Endometrial cancer may present with synchronous ovarian tumors, and distinguishing a primary ovarian cancer from endometrial metastasis has important staging and treatment implications. The recognition of metastatic disease to the ovary is critical because the prognosis and treatment are determined by the primary malignancy rather than the ovarian involvement.

<image>Panel A: Epithelial ovarian cancer subtypes showing high-grade serous (most common, fallopian tube origin, advanced at diagnosis), low-grade serous, endometrioid, clear cell, and mucinous with CA-125 elevation in 80 percent and typical vague presenting symptoms. Panel B: Germ cell tumor types showing dysgerminoma (most common malignant, radiosensitive, excellent prognosis), immature teratoma (graded by neuroepithelium), yolk sac tumor (AFP marker), and choriocarcinoma (beta-hCG marker) with fertility-sparing surgery approach. Panel C: Sex cord-stromal tumors showing granulosa cell (estrogen-producing, inhibin marker, late recurrence), Sertoli-Leydig cell (androgen-producing, virilization), and favorable prognosis with long-term surveillance requirement. Panel D: Metastatic tumors to ovary showing Krukenberg tumor (signet ring cells, gastric origin, bilateral), breast cancer metastasis, synchronous endometrial cancer, and principle that prognosis follows the primary malignancy.</image>

### Section 5: Ovarian Cancer Screening and Risk

Risk factors for ovarian cancer reflect both genetic predisposition and reproductive history. Advancing age is the most significant risk factor, with peak incidence occurring between ages 55 and 65. BRCA1 mutations confer a 35 to 46 percent lifetime risk, while BRCA2 mutations confer a 13 to 23 percent risk, together representing the strongest known genetic risk factors. A first-degree family history of ovarian cancer approximately triples the risk. Nulliparity is associated with increased risk, potentially through continuous ovulation without the protective interruption of pregnancy. Endometriosis is associated with an increased risk of clear cell and endometrioid subtypes specifically. Lynch syndrome, caused by mutations in mismatch repair genes, increases the risk of ovarian cancer along with endometrial and colorectal cancers.

Protective factors for ovarian cancer have been consistently identified in epidemiologic studies and inform risk counseling. Combined oral contraceptive use for 5 or more years reduces the risk of ovarian cancer by 30 to 50 percent, with protection persisting for decades after discontinuation. Each pregnancy reduces risk, likely through suppression of ovulation and exposure to progesterone. Breastfeeding provides additional risk reduction through prolongation of anovulation. Tubal ligation reduces risk by approximately 30 percent, possibly by preventing retrograde transport of potential carcinogens or inflammatory mediators. Bilateral salpingectomy at the time of other gynecologic surgery may provide an additional risk reduction benefit, particularly relevant given the growing evidence that high-grade serous carcinoma originates in the fimbriated end of the fallopian tube.

Population-based screening for ovarian cancer using CA-125 and transvaginal ultrasound is not recommended for average-risk women because available evidence has not demonstrated a mortality reduction. CA-125 lacks the specificity needed for a screening test, as it is elevated in numerous benign conditions and is normal in approximately 50 percent of stage I ovarian cancers, resulting in unacceptable false positive and false negative rates. Transvaginal ultrasound as a screening tool has a high false positive rate that leads to unnecessary surgical interventions. Large randomized controlled trials, including the UK Collaborative Trial of Ovarian Cancer Screening, did not demonstrate a statistically significant mortality reduction with multimodal screening. For high-risk women with BRCA mutations who decline risk-reducing surgery, screening with CA-125 and ultrasound every 6 months has been used, though its efficacy in improving outcomes remains unproven.

High-risk management for women with hereditary predisposition to ovarian cancer centers on risk-reducing bilateral salpingo-oophorectomy. For BRCA1 carriers, this procedure is recommended between ages 35 and 40 after completion of childbearing, while BRCA2 carriers may defer to ages 40 to 45 given the later average age of cancer onset. Risk-reducing surgery reduces ovarian cancer risk by approximately 80 percent and also reduces breast cancer risk in premenopausal BRCA carriers by eliminating ovarian estrogen production. Women who decline or defer surgery should be offered surveillance with CA-125 and transvaginal ultrasound every 6 months, though they should be counseled that this approach has not been proven to reduce mortality. The decision to pursue risk-reducing surgery should involve multidisciplinary counseling addressing the cancer risk, menopausal consequences, fertility implications, and psychological impact.

<image>Panel A: Ovarian cancer risk factors showing age (peak 55 to 65), BRCA1 (35 to 46 percent lifetime risk), BRCA2 (13 to 23 percent risk), first-degree family history (3-fold increase), nulliparity (continuous ovulation), endometriosis (clear cell and endometrioid subtypes), and Lynch syndrome. Panel B: Protective factors showing OCP use for 5 or more years (30 to 50 percent reduction), parity (each pregnancy reduces risk), breastfeeding (prolonged anovulation), tubal ligation (30 percent reduction), and bilateral salpingectomy (fallopian tube origin theory). Panel C: Screening limitations showing CA-125 (poor specificity, elevated in benign conditions, normal in 50 percent stage I), transvaginal ultrasound (high false positive rate), and UK CTOCS trial (no significant mortality reduction) with recommendation against average-risk screening. Panel D: High-risk management showing risk-reducing BSO timing (BRCA1 at 35 to 40, BRCA2 at 40 to 45), 80 percent ovarian cancer risk reduction, breast cancer risk reduction benefit, surveillance alternative for those declining surgery, and multidisciplinary counseling components.</image>

### Section 6: Evaluation of Adnexal Mass

Ultrasound characteristics provide the most important information for distinguishing benign from malignant adnexal masses. Benign features include a simple cystic appearance with thin, smooth walls, unilocular architecture without septations, the absence of solid components or papillary projections, minimal or no internal blood flow on Doppler, and mobility of the mass relative to surrounding structures. Malignant features include complex mixed cystic-solid morphology, thick irregular septations exceeding 3 millimeters, papillary excrescences projecting into the cyst cavity, increased and disordered vascularity with low-resistance arterial flow, and fixation to surrounding structures. The overall accuracy of transvaginal ultrasound in experienced hands approaches 90 percent for distinguishing benign from malignant masses, making it the most cost-effective initial evaluation tool.

Several risk stratification tools have been developed to improve the standardization and accuracy of adnexal mass assessment. The International Ovarian Tumor Analysis simple rules provide a set of ultrasound features classified as B-features (benign) and M-features (malignant) that allow classification of most masses without subjective pattern recognition. The Risk of Malignancy Index combines the menopausal status, ultrasound score, and CA-125 level into a composite score, with values above 200 conferring a high probability of malignancy. The Risk of Ovarian Malignancy Algorithm incorporates CA-125, HE4, and menopausal status into a calculated probability of malignancy. These tools assist in clinical decision-making but do not replace expert ultrasound interpretation, and their primary value is in standardizing the triage of patients to general gynecology versus gynecologic oncology.

Tumor markers complement imaging in the evaluation of adnexal masses and are selected based on the clinical scenario and suspected histologic type. CA-125 is the most commonly ordered marker and is elevated in approximately 80 percent of epithelial ovarian cancers, but its utility is limited by poor specificity, particularly in premenopausal women in whom endometriosis, pelvic inflammatory disease, and even menstruation can elevate levels. Alpha-fetoprotein is the marker for yolk sac tumors and is essential in the evaluation of young women with solid ovarian masses. Beta-human chorionic gonadotropin is associated with choriocarcinoma and should be measured in all reproductive-age women to exclude pregnancy and gestational trophoblastic disease. Inhibin is the marker for granulosa cell tumors, lactate dehydrogenase is elevated in dysgerminomas, and CA 19-9 may be elevated in mucinous tumors.

Referral to gynecologic oncology is indicated when clinical, imaging, and laboratory features suggest a significant probability of malignancy. A postmenopausal woman with an elevated CA-125 and a pelvic mass should be referred, as should any patient with a complex mass containing solid components, thick septations, or papillary projections. The presence of ascites, particularly in combination with an adnexal mass, warrants referral due to the high probability of advanced malignancy. Nodularity of the peritoneum detected on imaging suggests carcinomatosis and mandates oncologic evaluation. A strong family history of ovarian or breast cancer in the setting of an adnexal mass lowers the threshold for referral. Surgical staging and debulking performed by a gynecologic oncologist has been shown to improve survival outcomes in ovarian cancer compared to surgery performed by general gynecologists.

<image>Panel A: Benign versus malignant ultrasound features comparison showing benign (simple cyst, thin walls, unilocular, no blood flow, mobile) and malignant (complex cystic-solid, thick septations greater than 3 mm, papillary excrescences, increased vascularity, fixed) characteristics with 90 percent accuracy. Panel B: Risk stratification tools showing IOTA simple rules (B-features and M-features), Risk of Malignancy Index (menopausal status plus ultrasound score plus CA-125, threshold 200), and ROMA algorithm (CA-125 plus HE4 plus menopausal status). Panel C: Tumor markers by histologic type showing CA-125 (epithelial, poor specificity premenopausal), AFP (yolk sac), beta-hCG (choriocarcinoma), inhibin (granulosa cell), LDH (dysgerminoma), and CA 19-9 (mucinous). Panel D: Gynecologic oncology referral criteria showing postmenopausal with elevated CA-125 and mass, complex mass with solid components, ascites with adnexal mass, peritoneal nodularity, and family history of ovarian or breast cancer with improved survival when staged by oncologist.</image>

### Section 7: Management of Ovarian Cysts

Simple ovarian cysts in reproductive-age women are managed conservatively based on size and imaging characteristics. Cysts smaller than 5 centimeters are overwhelmingly functional and require no intervention, as they will resolve spontaneously in the vast majority of cases. Cysts between 5 and 7 centimeters warrant observation with repeat ultrasound in 6 to 12 weeks to confirm resolution or stability, and most will resolve within this timeframe. Cysts larger than 7 centimeters are considered for surgical evaluation due to the increased risk of torsion, the difficulty of definitively excluding neoplasia by imaging alone, and the reduced likelihood of spontaneous resolution. When a cyst resolves on follow-up imaging, no further workup is needed, and the patient can be reassured that functional cysts are a normal physiologic occurrence.

Simple cysts in postmenopausal women require a more cautious management approach due to the increased baseline risk of malignancy in this population. Very small cysts less than 1 centimeter may be observed without intervention, as they are common incidental findings with an extremely low malignancy risk. Cysts between 1 and 3 centimeters with simple morphology can be managed with ultrasound surveillance, typically repeated at 6-month intervals to confirm stability. Cysts larger than 3 centimeters or those with any concerning features warrant consideration for surgical evaluation, as the differential diagnosis in postmenopausal women includes both benign and malignant neoplasms. The threshold for surgical intervention is lower in postmenopausal women than in reproductive-age women, reflecting the shift in pretest probability toward neoplasia when ovulatory function has ceased.

Complex adnexal masses require careful evaluation and management that considers the specific imaging characteristics and clinical context. Masses with imaging features consistent with a dermoid, such as an echogenic nodule with acoustic shadowing, are managed surgically if larger than 5 centimeters or symptomatic, due to the risk of torsion and the low but not negligible possibility of malignant transformation. Endometriomas, recognized by their homogeneous low-level internal echoes (ground-glass appearance), may be managed medically with hormonal suppression or surgically depending on size, symptoms, and fertility considerations. Indeterminate complex masses that do not fit a characteristic pattern should undergo further evaluation with MRI, which can often provide a definitive diagnosis. Any mass with features suspicious for malignancy, including solid components, papillary projections, ascites, or increased vascularity, should be referred to gynecologic oncology for surgical evaluation.

Surgical options for ovarian cysts and masses are selected based on the preoperative assessment of malignancy risk, the patient's age, and reproductive goals. Laparoscopy is the preferred approach for masses that are presumed benign based on imaging and clinical criteria, offering shorter recovery, less pain, and reduced adhesion formation compared to laparotomy. Laparotomy with midline vertical incision is recommended when malignancy is suspected, as it provides the access necessary for comprehensive surgical staging and optimal debulking. Ovarian cystectomy, in which the cyst is removed while preserving the remaining ovarian tissue, is appropriate for benign lesions in reproductive-age women who wish to preserve fertility. Oophorectomy or salpingo-oophorectomy is preferred when malignancy cannot be excluded, in postmenopausal women, or when the ovarian tissue is significantly compromised by the pathology.

<image>Panel A: Reproductive-age simple cyst management showing less than 5 cm (observation, functional), 5 to 7 cm (repeat ultrasound in 6 to 12 weeks), greater than 7 cm (consider surgery for torsion risk), and resolution on follow-up (no further workup needed). Panel B: Postmenopausal simple cyst management showing less than 1 cm (observation), 1 to 3 cm (ultrasound surveillance every 6 months), greater than 3 cm (consider surgery), and lower intervention threshold due to higher malignancy pretest probability. Panel C: Complex mass management showing dermoid (surgery if greater than 5 cm or symptomatic), endometrioma (hormonal or surgical based on symptoms and fertility), indeterminate (MRI for characterization), and suspicious features (refer to gynecologic oncology). Panel D: Surgical approach selection showing laparoscopy (presumed benign, shorter recovery), laparotomy (suspected malignancy, midline vertical incision), cystectomy (fertility preservation, benign lesions), and oophorectomy (malignancy concern, postmenopausal, compromised ovary).</image>

### Section 8: Endometriomas

Endometriomas are ovarian cysts formed by the ectopic growth of endometrial tissue within the ovary, representing a common manifestation of endometriosis. The cysts contain old, degraded blood products that produce the characteristic dark brown, viscous fluid, giving rise to the term "chocolate cyst." On ultrasound, endometriomas demonstrate a distinctive homogeneous low-level echogenicity described as a ground-glass appearance, often with acoustic enhancement and no internal vascularity. Bilateral involvement is common, occurring in up to 50 percent of cases, and the presence of an endometrioma should prompt evaluation for deep infiltrating endometriosis and associated conditions including chronic pelvic pain, dysmenorrhea, dyspareunia, and infertility.

The diagnostic evaluation of endometriomas relies primarily on their characteristic imaging appearance, though additional studies may be helpful in atypical cases. Transvaginal ultrasound is highly accurate for diagnosing endometriomas, with the ground-glass pattern having high sensitivity and specificity. MRI is useful when the ultrasound appearance is atypical or when preoperative planning requires detailed assessment of deep endometriosis involving the rectovaginal septum, bladder, or ureters. CA-125 may be mildly elevated in the presence of endometriomas and active endometriosis, but its role in diagnosis is limited. Although the malignancy risk is very low at less than 1 percent, endometriomas are associated with an increased risk of clear cell and endometrioid ovarian carcinomas, and any atypical features on imaging should prompt further evaluation.

Treatment of endometriomas depends on the size of the cyst, the severity of symptoms, and the patient's reproductive goals. Small, asymptomatic endometriomas may be observed with serial imaging, particularly when the patient is not actively seeking pregnancy. Symptomatic endometriomas causing pain may be managed medically with hormonal therapy including combined oral contraceptive pills, progestin-only methods, or gonadotropin-releasing hormone agonists to suppress endometrial tissue growth. Surgical excision is indicated for large endometriomas, those causing significant symptoms unresponsive to medical therapy, or when tissue diagnosis is needed to exclude malignancy. The approach to endometriomas in the setting of infertility is nuanced, as surgery before in vitro fertilization remains controversial due to the potential for reduced ovarian reserve following cystectomy. Recurrence after surgical excision is common, occurring in approximately 20 to 30 percent of cases within 2 years.

Surgical management of endometriomas requires careful consideration of the impact on ovarian reserve, particularly in women of reproductive age who desire future fertility. Excisional cystectomy, in which the cyst wall is stripped from the normal ovarian cortex, is the preferred surgical technique as it provides tissue for histologic examination and has a lower recurrence rate than drainage and ablation. However, cystectomy inevitably removes some normal ovarian tissue along with the cyst wall, and this can result in a measurable reduction in anti-Mullerian hormone levels and antral follicle count on the affected ovary. The surgeon must balance complete cyst excision against preservation of ovarian tissue, and patients should be counseled about the potential impact on fertility before surgery. For women planning in vitro fertilization, oocyte retrieval from an ovary containing an endometrioma can be performed safely in most cases, and the decision to proceed with surgery versus direct IVF should be individualized.

<image>Panel A: Endometrioma features showing chocolate cyst gross appearance, ground-glass ultrasound pattern with homogeneous low-level echoes, bilateral occurrence in 50 percent of cases, and association with chronic pelvic pain, dysmenorrhea, dyspareunia, and infertility. Panel B: Diagnostic evaluation showing transvaginal ultrasound (high accuracy, ground-glass pattern), MRI (atypical cases, deep endometriosis mapping), CA-125 (mild elevation, limited diagnostic role), and malignancy risk (less than 1 percent, clear cell and endometrioid association). Panel C: Treatment decision algorithm showing observation (small, asymptomatic), medical therapy (hormonal suppression for pain), surgical excision (large, refractory, diagnostic need), controversial role before IVF, and 20 to 30 percent recurrence rate at 2 years. Panel D: Surgical considerations for ovarian reserve showing cystectomy technique (strip cyst wall from cortex), inevitable loss of normal ovarian tissue, measurable AMH and AFC reduction, surgeon balance of complete excision versus tissue preservation, and individualized decision-making for IVF candidates.</image>

### Section 9: Ovarian Torsion

Ovarian torsion is a gynecologic surgical emergency in which the ovary, and frequently the fallopian tube, twists on its vascular pedicle, compromising blood flow and leading to tissue ischemia and potential infarction. The most significant risk factor is an ovarian mass between 5 and 8 centimeters in diameter, which is large enough to increase the weight and mobility of the ovary but not so large as to become fixed in the pelvis. Pregnancy increases torsion risk due to corpus luteum cyst development and hormonal effects on ovarian ligament laxity. Ovulation induction therapy enlarges the ovaries and significantly increases torsion risk, particularly in the setting of ovarian hyperstimulation syndrome. Torsion can occur at any age but is most common in reproductive-age women, and prior torsion confers an increased risk of recurrence on the same side.

The clinical presentation of ovarian torsion is characterized by sudden, severe, unilateral lower abdominal or pelvic pain. Nausea and vomiting frequently accompany the pain, reflecting the vagal response to peritoneal irritation and ischemia. A distinctive feature of torsion is the waxing and waning nature of pain in some patients, reflecting intermittent torsion in which the ovary twists and partially untwists, producing episodic symptoms. An adnexal mass may be palpable on examination, and the affected side is typically exquisitely tender to palpation. Laboratory studies are nonspecific, with a mild leukocytosis sometimes present but not diagnostic. The differential diagnosis includes ruptured ovarian cyst, ruptured ectopic pregnancy, appendicitis, and tubo-ovarian abscess.

The diagnosis of ovarian torsion relies on a combination of clinical suspicion and imaging findings, with the understanding that no single test definitively confirms or excludes the diagnosis. Transvaginal ultrasound demonstrates an enlarged ovary, often with peripheral displacement of follicles to the cortex and stromal edema. Doppler evaluation may show decreased or absent arterial and venous flow to the affected ovary, which is highly suggestive of torsion. However, the presence of normal Doppler flow does not exclude torsion, as intermittent twisting may allow periods of normal perfusion, and dual blood supply from the ovarian and uterine arteries may partially maintain flow. Given the limitations of imaging, clinical suspicion should drive the decision to proceed with surgical exploration, and delay should be avoided to maximize the chance of ovarian salvage.

Management of ovarian torsion requires prompt surgical intervention, with detorsion (untwisting) as the primary goal to preserve ovarian function. Laparoscopy is the preferred surgical approach and should be performed urgently once torsion is suspected. Upon visualization, the adnexa are untwisted regardless of the appearance of the ovary, as even dusky or dark-appearing ovaries have been shown to recover function in the majority of cases after restoration of blood flow. Oophoropexy, the surgical fixation of the ovary to the pelvic sidewall, may be performed to prevent recurrence, though its efficacy is not definitively established. Any underlying ovarian mass, such as a dermoid or cystadenoma, is managed concurrently with cystectomy after detorsion. Oophorectomy is reserved for cases in which the ovary is clearly necrotic and nonviable, which is a clinical judgment made at the time of surgery.

<image>Panel A: Ovarian torsion risk factors showing ovarian mass 5 to 8 cm (highest risk), pregnancy (corpus luteum, ligament laxity), ovulation induction (enlarged ovaries, OHSS), reproductive age (most common), and prior torsion (recurrence risk). Panel B: Clinical presentation showing sudden severe unilateral pain, nausea and vomiting (vagal response), waxing and waning pattern (intermittent torsion), palpable tender adnexal mass, and differential diagnosis (ruptured cyst, ectopic, appendicitis, TOA). Panel C: Diagnostic evaluation showing ultrasound findings (enlarged ovary, peripheral follicles, stromal edema), Doppler (decreased or absent flow suggestive but normal flow does not exclude), and principle that clinical suspicion drives surgical decision without delay. Panel D: Surgical management showing laparoscopic detorsion (primary goal, untwist regardless of appearance), ovarian recovery even if dusky, oophoropexy (prevent recurrence), concurrent cystectomy for underlying mass, and oophorectomy reserved for clearly necrotic tissue.</image>

### Section 10: Other Pelvic Masses

Uterine leiomyomas are the most common pelvic tumors in women, with a prevalence of 70 to 80 percent by age 50, and they frequently present as pelvic masses that must be distinguished from adnexal pathology. On ultrasound, fibroids appear as solid, well-circumscribed, hypoechoic masses with a characteristic whorled internal architecture and variable degrees of calcification and degeneration. Large subserosal or pedunculated fibroids may mimic solid ovarian masses on imaging, and MRI or careful ultrasound evaluation may be needed to confirm the uterine origin. Symptoms include heavy menstrual bleeding, particularly from submucosal fibroids, pelvic pressure and urinary frequency from bulk effect, and reproductive complications including infertility and recurrent pregnancy loss. Management ranges from observation for asymptomatic fibroids through medical therapy, procedural options including uterine artery embolization, and surgical treatment with myomectomy or hysterectomy.

Paratubal cysts are fluid-filled cysts that arise from Mullerian or Wolffian duct remnants and are located adjacent to the fallopian tube and ovary. These cysts are typically small, simple, and asymptomatic, discovered incidentally during surgery or imaging. They are virtually always benign and do not require treatment unless they become large enough to cause symptoms or increase the risk of torsion. Paratubal cysts may be difficult to distinguish from ovarian cysts on imaging, particularly when they are closely apposed to the ovary, and the distinction is often made only at the time of surgery. Simple paratubal cysts that are stable in size on serial imaging require no further intervention.

Peritoneal inclusion cysts are pseudocysts that form when physiologic peritoneal fluid becomes trapped by adhesions surrounding the ovary, creating a fluid collection that conforms to the peritoneal surface rather than forming a discrete round cyst. These cysts are associated with a history of prior pelvic surgery, pelvic inflammatory disease, or endometriosis, all of which produce intraperitoneal adhesions. The characteristic imaging appearance shows a fluid collection that conforms to the surrounding structures with the ovary often visible at the periphery of or within the collection. Treatment may include observation for asymptomatic collections, percutaneous drainage for symptomatic relief, or surgical adhesiolysis and excision for recurrent or symptomatic disease. Hormonal suppression of ovulation may reduce fluid production and prevent recurrence in some patients.

Non-gynecologic pelvic masses must always be considered in the differential diagnosis, as gastrointestinal and urinary tract pathology may present with pelvic mass or pain. Appendiceal pathology, including acute appendicitis and appendiceal abscess, presents with right lower quadrant pain, fever, and leukocytosis and may be confused with right ovarian pathology, particularly in young women. Diverticular disease and diverticular abscess present with left lower quadrant pain and are more common in older patients. Gastrointestinal malignancy, particularly colorectal cancer, may present as a pelvic mass with associated irregular margins, ascites, and constitutional symptoms. A distended urinary bladder may be palpable as a midline pelvic mass and should be excluded by catheterization before attributing a midline mass to gynecologic pathology.

<image>Panel A: Uterine leiomyomas showing solid whorled hypoechoic ultrasound appearance, pedunculated subserosal type mimicking ovarian mass, symptom spectrum (heavy bleeding, bulk symptoms, reproductive complications), and management options from observation through medical therapy to surgery. Panel B: Paratubal cysts showing location adjacent to fallopian tube and ovary, Mullerian or Wolffian duct remnant origin, typically simple and asymptomatic, difficult distinction from ovarian cysts on imaging, and benign natural history requiring no intervention unless symptomatic. Panel C: Peritoneal inclusion cysts showing adhesion-trapped peritoneal fluid conforming to surrounding structures, association with prior surgery, PID, and endometriosis, ovary visible at periphery, and management options (observation, drainage, adhesiolysis, hormonal suppression). Panel D: Non-gynecologic pelvic masses showing appendiceal pathology (right lower quadrant, fever, young women), diverticular disease (left lower quadrant, older patients), colorectal cancer (irregular mass, ascites, constitutional symptoms), and distended bladder (midline mass, catheterization to exclude).</image>

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## Summary

- The pelvic mass differential includes ovarian, uterine, tubal, gastrointestinal, and urinary tract origins, with age as a key factor in determining malignancy risk
- Functional cysts (follicular, corpus luteum, hemorrhagic) are common in reproductive-age women and resolve within 1 to 3 cycles without intervention
- Mature cystic teratoma (dermoid) contains tissue from all three germ layers and is managed with cystectomy when larger than 5 cm or symptomatic
- Ovarian cancer risk factors include age, BRCA mutations, nulliparity, and family history, with OCPs, parity, and salpingectomy as protective factors
- Population-based ovarian cancer screening is not recommended for average-risk women due to lack of mortality benefit
- Malignant ultrasound features include solid components, thick septations, papillary projections, increased vascularity, and ascites
- CA-125 is elevated in 80 percent of epithelial ovarian cancers but lacks specificity, particularly in premenopausal women
- Postmenopausal women with pelvic masses have a lower threshold for surgical intervention due to higher malignancy pretest probability
- Ovarian torsion presents with sudden severe unilateral pain and nausea, requires emergent surgical detorsion, and ovarian salvage is prioritized
- Endometriomas demonstrate ground-glass ultrasound pattern and carry considerations for ovarian reserve impact with surgical management

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## Key Terms

| Term | Definition |
|------|------------|
| Functional cyst | Non-neoplastic ovarian cyst |
| Dermoid | Mature cystic teratoma |
| CA-125 | Tumor marker for epithelial ovarian cancer |
| BRCA | Breast cancer gene; increases ovarian cancer risk |
| Torsion | Twisting of ovary on its pedicle |
| Endometrioma | Ovarian cyst from endometriosis |
| Cystadenoma | Benign epithelial ovarian tumor |
| Meigs syndrome | Fibroma with ascites and pleural effusion |

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