Residency · Residency · General Surgery
Non-Melanoma Skin Cancer: Surgical Management
Introduction
Non-melanoma skin cancers (NMSCs) are the most common malignancies worldwide, with over 5 million cases diagnosed annually in the United States. Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) account for the vast majority. While mortality is low, these tumors carry significant morbidity through local tissue destruction, and high-risk SCC can metastasize. The general surgeon should be competent in diagnosis, excision, and recognition of high-risk features requiring multidisciplinary care.
Epidemiology and Risk Factors
Basal cell carcinoma accounts for approximately 80% of NMSC and rarely metastasizes (less than 0.1%). Squamous cell carcinoma accounts for approximately 20% and has a metastatic rate of 2-6% overall, higher for high-risk lesions. Ultraviolet radiation is the most important modifiable risk factor: UVB (290-320 nm) causes direct DNA damage through pyrimidine dimers, while UVA (320-400 nm) causes indirect oxidative damage. Cumulative exposure correlates with SCC risk, while intermittent intense exposure correlates with BCC risk. Fitzpatrick skin types I-II (fair skin, light eyes, tendency to burn) confer increased risk. Immunosuppression is a major risk factor, with organ transplant recipients having a 65-250 fold increased risk of SCC and the SCC:BCC ratio reversing compared to the general population. Marjolin ulcer refers to SCC arising in chronic wounds, burn scars, or draining sinuses. Additional risk factors include arsenic exposure, HPV infection (particularly types 5 and 8 in epidermodysplasia verruciformis), and ionizing radiation. Genetic syndromes include Gorlin syndrome (basal cell nevus syndrome, PTCH1 mutation) and xeroderma pigmentosum.
Basal Cell Carcinoma
Subtypes and Clinical Features
Nodular BCC is the most common subtype (60%) and presents as a pearly, translucent papule or nodule with rolled borders, central ulceration, and arborizing telangiectasias. Superficial BCC presents as a thin, erythematous, scaly plaque common on the trunk and is often multifocal. Morpheaform or infiltrative BCC presents as a scar-like, ill-defined plaque with an aggressive local growth pattern and higher recurrence rates. Pigmented BCC contains melanin and must be distinguished from melanoma clinically.
Surgical Treatment of BCC
Standard surgical excision with 4 mm clinical margins for well-defined tumors smaller than 2 cm achieves a 95% cure rate. Mohs micrographic surgery is indicated for high-risk locations (face, ears, eyelids, nose), recurrent tumors, morpheaform or infiltrative subtypes, and tumors in areas where tissue conservation is critical, achieving a cure rate exceeding 99%. Curettage and electrodesiccation is appropriate for small, low-risk nodular or superficial BCCs on the trunk or extremities but is not appropriate for morpheaform subtypes. Nonsurgical options include topical imiquimod or 5-fluorouracil for superficial BCC, photodynamic therapy, and cryotherapy for select small lesions. For advanced or metastatic BCC, Hedgehog pathway inhibitors (vismodegib, sonidegib) are used for locally advanced or metastatic disease, and anti-PD-1 immunotherapy (cemiplimab) is available for Hedgehog inhibitor-refractory cases.
<image>Clinical photographs showing the four major subtypes of basal cell carcinoma: nodular with pearly rolled border and telangiectasias, superficial with erythematous scaly plaque, morpheaform with scar-like ill-defined plaque, and pigmented with melanin deposits, each with labeled distinguishing features</image>
Squamous Cell Carcinoma
Clinical Spectrum
Actinic keratosis is a premalignant lesion presenting as a rough, scaly papule on sun-exposed skin with a 5-10% lifetime risk of progression to SCC. SCC in situ (Bowen disease) represents full-thickness epidermal atypia without dermal invasion and presents as a well-defined erythematous plaque. Invasive SCC is a firm, keratinizing nodule or plaque that may ulcerate and can arise de novo or from precursors. Keratoacanthoma is a rapidly growing, dome-shaped nodule with a central keratin plug, considered a well-differentiated SCC variant that may spontaneously regress, though excision is recommended.
High-Risk Features for SCC
Tumor factors that confer high risk include size greater than 2 cm, depth greater than 6 mm or invasion beyond subcutaneous fat, poorly differentiated histology, perineural invasion, lymphovascular invasion, and desmoplastic growth pattern. High-risk locations include the ear, lip, temple, scalp, and non-sun-exposed sites. Patient factors include immunosuppression, recurrent tumors, tumors arising in chronic wounds (Marjolin ulcer), and tumors in prior radiation fields. The BWH (Brigham and Women's Hospital) staging system may better stratify risk than the AJCC for cutaneous SCC.
Surgical Treatment of SCC
Standard surgical excision uses 4-6 mm margins for low-risk tumors and wider margins of 6-10 mm for high-risk features. Mohs micrographic surgery is recommended for high-risk SCCs, particularly in the head and neck region, recurrent tumors, and tumors with perineural invasion. Sentinel lymph node biopsy is increasingly considered for high-risk SCC (BWH T2b/T3), though data is evolving and it is not yet standard of care. Lymph node dissection is indicated for clinically or radiologically positive regional lymph nodes. Adjuvant radiation is indicated for positive margins when re-excision is not feasible, extensive perineural invasion, and regional nodal metastases. Cemiplimab (anti-PD-1) is FDA-approved for locally advanced or metastatic cutaneous SCC not amenable to surgery or radiation.
<image>Diagram illustrating the surgical margins and depth of excision for squamous cell carcinoma, showing low-risk versus high-risk tumors with appropriate margin widths, depth of invasion measurement from the granular layer, and the distinction between Breslow thickness and Clark level equivalents</image>
Other Non-Melanoma Skin Cancers
Merkel cell carcinoma is a rare, aggressive neuroendocrine tumor associated with Merkel cell polyomavirus (80% of cases), treated with wide excision using 1-2 cm margins plus sentinel lymph node biopsy, adjuvant radiation, and checkpoint inhibitors (avelumab, pembrolizumab) for advanced disease. Dermatofibrosarcoma protuberans is locally aggressive but rarely metastasizes, is characterized by COL1A1-PDGFB fusion, and is treated with wide excision using 2-3 cm margins or Mohs surgery, with imatinib available for unresectable disease. Sebaceous carcinoma is an aggressive tumor of sebaceous glands, most commonly periocular, and is associated with Muir-Torre syndrome (a Lynch syndrome variant).
Reconstruction After Excision
Primary closure is preferred when possible with minimal tension. Secondary intention is appropriate for concave surfaces such as the medial canthus, nasal alar crease, and temple. Full-thickness skin grafts are used for small facial defects and split-thickness grafts for larger defects. Local flaps including rotation, advancement, and transposition flaps are used for larger defects, and Z-plasty is available for scar revision. Free tissue transfer is rarely needed and is reserved for extensive composite defects.
<image>Reconstructive ladder for facial skin cancer defects showing primary closure, secondary intention healing, full-thickness skin graft, and common local flap options including rotation flap, advancement flap, and bilobed flap with step-by-step surgical planning illustrations</image>
Surveillance
Low-risk NMSC requires annual full skin examination. High-risk SCC warrants follow-up every 3-6 months for 2 years, then every 6-12 months for 3 years, and then annually, with regional lymph node examination included. Immunosuppressed patients require surveillance every 3-6 months indefinitely, with consideration of reducing immunosuppression in transplant patients with multiple SCCs (coordinated with the transplant team). Patient education on sun protection, self-examination, and prompt reporting of new lesions is essential.
Key Clinical Pearls
Any non-healing ulcer, nodule, or changing skin lesion should be biopsied, with a low threshold especially in immunosuppressed patients. Morpheaform BCC has clinically indistinct borders and requires Mohs surgery or wide margins due to high recurrence rates. High-risk SCC features (greater than 2 cm, poorly differentiated, perineural invasion, immunosuppression) significantly increase metastatic risk and warrant more aggressive treatment. Organ transplant recipients require lifelong dermatologic surveillance and consideration of immunosuppression reduction for recurrent SCC. Marjolin ulcers arising in chronic wounds are aggressive SCCs with high metastatic potential.
References
- Work Group; Invited Reviewers, Kim JYS, Kozlow JH, et al. Guidelines of care for the management of basal cell carcinoma. J Am Acad Dermatol. 2018;78(3):540-559.
- Work Group; Invited Reviewers, Alam M, Ratner D, et al. Guidelines of care for the management of cutaneous squamous cell carcinoma. J Am Acad Dermatol. 2018;78(3):560-578.
- Migden MR, Rischin D, Schmults CD, et al. PD-1 blockade with cemiplimab in advanced cutaneous squamous-cell carcinoma. N Engl J Med. 2018;379(4):341-351.
- Karia PS, Han J, Schmults CD. Cutaneous squamous cell carcinoma: estimated incidence of disease, nodal metastasis, and deaths from disease in the United States, 2012. J Am Acad Dermatol. 2013;68(6):957-966.
