# Clinical Cases: Neoplasia - Clinical Aspects

## Case 1: Breast Cancer with Paraneoplastic Hypercalcemia

### Patient Demographics
- **Age:** 62 years old
- **Sex:** Female
- **Occupation:** Retired teacher

### Chief Complaint
"Confusion, fatigue, and excessive thirst for 2 weeks"

### History of Present Illness
A 62-year-old female is brought to the emergency department by her daughter due to progressive confusion and lethargy over the past 2 weeks. The daughter reports that her mother has been complaining of increased thirst, frequent urination, constipation, and nausea. She has also noted significant fatigue and weakness. The patient has a history of breast cancer diagnosed 3 years ago, treated with mastectomy followed by chemotherapy. She was in remission but has not had imaging in 6 months. She reports increasing back pain over the past month.

### Physical Examination
- **Vital Signs:** BP 110/68 mmHg, HR 92 bpm, RR 18/min, Temp 37.2C
- **General:** Appears lethargic, oriented to person only, dry mucous membranes
- **Cardiovascular:** Regular rhythm, normal S1/S2, no murmurs
- **Respiratory:** Clear to auscultation bilaterally
- **Abdomen:** Soft, mild tenderness throughout, decreased bowel sounds
- **Musculoskeletal:** Point tenderness over thoracic and lumbar spine
- **Neurologic:** Altered mental status, decreased concentration, proximal muscle weakness

### Diagnostic Workup

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| Calcium (total) | 14.8 mg/dL | 8.5-10.5 mg/dL |
| Ionized calcium | 1.85 mmol/L | 1.12-1.32 mmol/L |
| PTH | 8 pg/mL | 10-65 pg/mL |
| PTHrP | 85 pmol/L | <2 pmol/L |
| Creatinine | 1.8 mg/dL | 0.7-1.3 mg/dL |
| CA 15-3 | 285 U/mL | <30 U/mL |
| Alkaline phosphatase | 320 U/L | 44-147 U/L |

**Imaging:**
- **CT Chest/Abdomen/Pelvis:** Multiple pulmonary nodules, hepatic lesions, and suspicious lymphadenopathy
- **Bone Scan:** Widespread skeletal metastases involving spine, ribs, pelvis, and proximal femurs
- **MRI Spine:** Multiple lytic lesions throughout thoracic and lumbar spine

**Tumor Markers:**
| Marker | Result | Clinical Significance |
|--------|--------|----------------------|
| CA 15-3 | 285 U/mL | Elevated; monitoring breast cancer |
| CEA | 12.5 ng/mL | Mildly elevated |

### Pathology Correlation
This case demonstrates **paraneoplastic syndrome** and **tumor marker** utility:

**Hypercalcemia of Malignancy:**
Two main mechanisms:
1. **Humoral hypercalcemia of malignancy (HHM):**
   - Tumor produces PTHrP (parathyroid hormone-related peptide)
   - PTHrP mimics PTH effects: increases bone resorption, renal calcium reabsorption
   - Common in squamous cell carcinomas, breast cancer, renal cell carcinoma
   - PTH is suppressed (distinguishing from primary hyperparathyroidism)

2. **Local osteolytic hypercalcemia:**
   - Direct bone destruction by metastases
   - Tumor cells produce factors (IL-1, TNF, RANK-L) stimulating osteoclasts
   - Common with breast cancer, multiple myeloma

**Clinical Features of Hypercalcemia ("Stones, Bones, Moans, Groans, Psychiatric Overtones"):**
- Stones: Nephrolithiasis, nephrocalcinosis
- Bones: Bone pain, pathologic fractures
- Moans: Abdominal pain, constipation
- Groans: Nausea, vomiting
- Psychiatric overtones: Confusion, lethargy, depression

**Tumor Markers:**
- **CA 15-3:** Monitoring breast cancer (not for screening)
- Rising levels suggest disease progression/recurrence
- Useful for treatment response assessment

### Clinical Image
![Breast Carcinoma - Gross Pathology](case_01_image.jpg)

*Gross pathology of invasive breast carcinoma showing a stellate, firm, white mass with irregular borders characteristic of infiltrating ductal carcinoma. The spiculated margins represent tumor invasion into surrounding breast tissue.*

**Image Source:** Wikimedia Commons - "Breast cancer"
**License:** CC BY-SA 3.0
**URL:** https://commons.wikimedia.org/wiki/File:CA_Breast_Macro.jpg

### Diagnosis
**Metastatic Breast Cancer with Paraneoplastic Hypercalcemia of Malignancy**
- TNM Stage: Stage IV (M1 - distant metastases)

### Treatment
**Immediate (Hypercalcemia):**
1. Aggressive IV fluid resuscitation (normal saline)
2. IV bisphosphonate (zoledronic acid or pamidronate)
3. Consider denosumab if bisphosphonate-refractory
4. Calcitonin for rapid initial effect
5. Treat underlying malignancy

**Oncologic:**
1. Restage disease with tissue confirmation if possible
2. Tumor profiling (ER/PR, HER2 status)
3. Systemic therapy based on receptor status
4. Bone-modifying agents (ongoing bisphosphonate or denosumab)
5. Radiation therapy for painful bone metastases

### Teaching Points
1. **Paraneoplastic syndromes** are clinical manifestations not caused by direct tumor invasion
2. **Hypercalcemia** is the most common paraneoplastic syndrome; PTHrP-mediated (humoral) vs. local osteolytic
3. Suppressed PTH with elevated calcium suggests malignancy-related hypercalcemia
4. **Tumor markers** are most valuable for monitoring disease, not screening
5. **TNM staging** is the most important prognostic factor for solid tumors
6. Stage IV disease indicates distant metastasis regardless of T and N status

---

## Case 2: Small Cell Lung Cancer with SIADH and Paraneoplastic Syndrome

### Patient Demographics
- **Age:** 67 years old
- **Sex:** Male
- **Occupation:** Former construction worker

### Chief Complaint
"Cough, weakness, and confusion for 3 weeks"

### History of Present Illness
A 67-year-old male with a 50 pack-year smoking history presents with a 3-week history of productive cough, progressive weakness, and confusion. His family reports he has been increasingly disoriented and has fallen twice at home. He has lost 7 kg over the past 2 months. He initially attributed symptoms to a respiratory infection but has worsened despite antibiotics. He also notes difficulty rising from a chair and climbing stairs.

### Physical Examination
- **Vital Signs:** BP 136/82 mmHg, HR 78 bpm, RR 20/min, Temp 37.0C, SpO2 94% on room air
- **General:** Thin male, appears confused, no acute distress
- **HEENT:** Moist mucous membranes, no signs of dehydration
- **Respiratory:** Decreased breath sounds in right upper lobe, no wheezing
- **Neurologic:** Oriented to person only, proximal muscle weakness (4/5 in shoulders and hips), strength improves slightly with repeated testing, deep tendon reflexes diminished
- **No edema**

### Diagnostic Workup

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| Sodium | 118 mEq/L | 136-145 mEq/L |
| Serum osmolality | 248 mOsm/kg | 280-300 mOsm/kg |
| Urine osmolality | 520 mOsm/kg | 50-1200 mOsm/kg |
| Urine sodium | 85 mEq/L | Variable |
| TSH | 2.1 mU/L | 0.5-5.0 mU/L |
| Cortisol (AM) | 18 mcg/dL | 5-25 mcg/dL |

**Imaging:**
- **Chest X-ray:** Large right hilar mass with mediastinal widening
- **CT Chest:** 6 cm right hilar mass encasing right mainstem bronchus, extensive mediastinal lymphadenopathy, small bilateral pleural effusions
- **MRI Brain:** Multiple small enhancing lesions consistent with metastases

**Bronchoscopy with Biopsy:**
- Endobronchial tumor obstructing right upper lobe bronchus
- Pathology: Small cell carcinoma, positive for synaptophysin, chromogranin, CD56

**Electrophysiology:**
- EMG showing incremental response to repetitive nerve stimulation (characteristic of Lambert-Eaton)

**Antibody Testing:**
- Anti-voltage-gated calcium channel (VGCC) antibodies: Positive

### Pathology Correlation
This case demonstrates **multiple paraneoplastic syndromes** associated with small cell lung cancer:

**1. SIADH (Syndrome of Inappropriate ADH Secretion):**
- Ectopic production of ADH (vasopressin) by tumor cells
- Causes water retention and dilutional hyponatremia
- Key features: Euvolemia, low serum osmolality, inappropriately concentrated urine
- Must exclude other causes of hyponatremia

**2. Lambert-Eaton Myasthenic Syndrome (LEMS):**
- Antibodies against voltage-gated calcium channels (VGCCs)
- Antibodies produced against tumor antigens cross-react with nerve terminals
- Causes impaired acetylcholine release at neuromuscular junction
- Key features: Proximal weakness, autonomic dysfunction, **improvement with repeated activity** (unlike myasthenia gravis)

**Small Cell Carcinoma Characteristics:**
- Neuroendocrine tumor (positive for synaptophysin, chromogranin)
- Highly aggressive, early metastasis
- Strong association with smoking
- Most common to produce paraneoplastic syndromes
- Staging: Limited vs. Extensive disease

**Other SCLC Paraneoplastic Syndromes:**
- Ectopic ACTH (Cushing syndrome)
- Anti-Hu antibodies (limbic encephalitis, sensory neuropathy)
- Cerebellar degeneration

### Clinical Image
![Small Cell Lung Carcinoma](case_02_image.jpg)

*Histopathology of small cell lung carcinoma showing sheets of small cells with scant cytoplasm, hyperchromatic nuclei with finely granular "salt and pepper" chromatin, nuclear molding, and frequent mitotic figures. Neuroendocrine markers are typically positive.*

**Image Source:** Wikimedia Commons - "Small cell lung cancer"
**License:** CC BY-SA 3.0
**URL:** https://commons.wikimedia.org/wiki/File:Small_cell_lung_cancer_-_cytology.jpg

### Diagnosis
1. **Extensive-Stage Small Cell Lung Cancer** (brain metastases)
2. **SIADH** (paraneoplastic)
3. **Lambert-Eaton Myasthenic Syndrome** (paraneoplastic)

### Treatment
**SIADH Management:**
1. Fluid restriction (500-1000 mL/day)
2. Salt tablets if tolerated
3. Consider tolvaptan (vasopressin receptor antagonist) if severe
4. Treat underlying cancer

**LEMS Management:**
1. Treat underlying cancer (primary therapy)
2. 3,4-diaminopyridine to enhance acetylcholine release
3. Pyridostigmine as adjunct
4. IVIG or plasmapheresis if severe

**Oncologic Treatment:**
1. Chemotherapy (platinum-etoposide) with immunotherapy
2. Prophylactic cranial irradiation (if response to chemotherapy)
3. Whole brain radiation for brain metastases
4. Palliative care integration

### Teaching Points
1. **Small cell lung cancer** is the tumor most frequently associated with paraneoplastic syndromes
2. **SIADH** causes euvolemic hyponatremia with inappropriately concentrated urine
3. **Lambert-Eaton syndrome** features proximal weakness that improves with activity (presynaptic NMJ disorder)
4. Paraneoplastic syndromes may precede cancer diagnosis and resolve with successful treatment
5. Recognition of paraneoplastic syndromes should prompt thorough malignancy workup
6. **Cancer screening** (low-dose CT for lung cancer) can detect cancers at earlier, more treatable stages