Cutaneous Tumors and Lymphoproliferative Disorders
Domain 5 tests whether you can separate benign, premalignant and malignant lesions and choose the right biopsy and margin.
Keratinocytic tumours
- Basal cell carcinoma: pearly, telangiectatic, rolled edge; histology shows peripheral palisading and clefting. Morpheaform lesions are ill-defined and need Mohs.
- Squamous cell carcinoma: keratotic, ulcerated, sun-exposed; keratin pearls on histology. High-risk features are depth, perineural invasion and immunosuppression. Bowen disease is in situ.
- Actinic keratosis: rough scale and field cancerization; cryotherapy, 5-fluorouracil, imiquimod or photodynamic therapy.
Melanoma
- ABCDE and ugly-duckling sign. Subtypes: superficial spreading, nodular, lentigo maligna, acral lentiginous (acral sites in darker skin).
- Breslow thickness drives margins and sentinel node biopsy, considered at 0.8 mm or more or when ulcerated. Clark level is descriptive only.
Other tumours and lymphocytes
- Dermatofibroma (dimple sign), seborrheic keratosis, epidermal cyst, lipoma.
- Mycosis fungoides: patches and plaques, epidermotropism, Pautrier microabscesses, CD4+ clone; Sezary syndrome is leukaemic.
- Kaposi sarcoma (HHV-8), B-cell lymphoma, mastocytosis.
Worked example
A 52-year-old has a 1.2 mm Breslow melanoma on the back after excision biopsy. Management is wide local excision with a 1-2 cm margin plus sentinel lymph node biopsy. Reasoning: Breslow 1.01-2 mm meets sentinel node criteria; margin depends on thickness, not on original biopsy size.
Traps
Never shave a suspected melanoma. Do not use Clark level to decide sentinel node biopsy. Do not call a rapidly growing keratoacanthoma benign without histology.