Skin Tumours and Dermato-oncology
Malignant tumours
Basal cell carcinoma is the commonest skin cancer: pearly rolled edge, telangiectasia, ulceration; dermoscopy shows arborising vessels and blue-grey ovoid nests. It rarely metastasises but is locally destructive. Squamous cell carcinoma arises on sun-damaged skin or within Bowen disease; it is keratotic, tender, and can metastasise, especially on ear and lip and in immunosuppressed patients. Melanoma: apply ABCDE and the seven-point checklist (majors - change in size, shape, colour; minors - diameter over 6 mm, inflammation, oozing, altered sensation). Breslow thickness drives prognosis and margin; Clark level is historical.
Benign mimics
Seborrhoeic keratosis: stuck-on, comedo-like openings, cerebriform pattern. Dermatofibroma: firm nodule with dimple sign. Keratoacanthoma: rapid keratin crater on sun-exposed skin.
Margins and management
Suspected melanoma: excision biopsy with 2 mm margin - never a shave. Subsequent wide local excision depends on Breslow (about 0.5–1 cm for thin lesions, 2 cm for deeper). Low-risk BCC: 3–4 mm clinical margins; high-risk, recurrent or cosmetically critical: Mohs micrographic surgery. SCC: 4–6 mm; high-risk features need nodal assessment.
Traps
- Assuming every pigmented lesion is melanocytic - amelanotic melanoma is a classic miss.
- Quoting Clark level where Breslow is asked for.
- Cryotherapy of a keratoacanthoma-like lesion without histology.
- Forgetting that transplant recipients develop multiple aggressive SCCs.
Rule of thumb
A lesion that is new, changing, bleeding or non-healing after 6–8 weeks should be biopsied or referred - do not reassure on appearance alone.