Cutaneous and Soft Tissue Lesions of the Head and Neck
Core concepts
Focus on diagnosis and margin strategy for cutaneous malignancy. Know basal cell carcinoma subtypes (nodular, morpheaform, basosquamous) and their behavior; squamous cell carcinoma risk factors (immunosuppression, radiation, chronic wounds) and high-risk features (depth, perineural invasion, poor differentiation, ear/lip location). Understand melanoma: Breslow thickness, ulceration, mitotic rate, sentinel lymph node biopsy thresholds, and margins by thickness. Know Mohs micrographic surgery indications (high-risk location, recurrent, ill-defined, tissue-sparing needs) and when to use frozen vs permanent sections. Recognize benign mimics (keratoacanthoma, seborrheic keratosis, atypical fibroxanthoma) and dermatofibrosarcoma protuberans behavior.
Traps
Questions test margin adequacy versus function in cosmetically sensitive areas, and when sentinel node biopsy is indicated. A common trap is assuming all SCC needs the same margins-high-risk lesions require wider margins and consideration of nodal evaluation. Another is confusing perineural invasion (higher recurrence, may need radiation) with perineural spread. Know that morpheaform BCC has subclinical extension and needs Mohs or wide margins.
Worked example / rule of thumb
Melanoma on the ear, Breslow 1.2 mm, ulcerated: wide local excision with 1–2 cm margins and offer sentinel lymph node biopsy. Rule of thumb: high-risk location + ill-defined histology → Mohs; melanoma → margins by Breslow plus nodal staging when indicated.