Cutaneous Tumors and Dermatopathology
Melanocytic lesions
Benign nevi vs melanoma: ABCDE and histologic criteria (asymmetry, border, color, diameter, evolution). Breslow thickness drives staging and prognosis. Dysplastic nevi show architectural and cytologic atypia but lack pagetoid spread and mitoses.
Keratinocytic tumors
Actinic keratosis (premalignant), basal cell carcinoma (pearly, telangiectasia, palisading, clefting), squamous cell carcinoma (keratin pearls, atypia), and keratoacanthoma. Basosquamous and microcystic variants appear in pathology stems.
Adnexal and soft tissue tumors
Sebaceous adenoma (Muir-Torre), trichilemmoma (Cowden), dermatofibroma (dimple sign), dermatofibrosarcoma protuberans (CD34+, storiform), and lipoma.
Vascular and lymphoid
Pyogenic granuloma, Kaposi sarcoma (HHV-8), angiosarcoma, and cutaneous lymphoma (mycosis fungoides: epidermotropism, Pautrier microabscesses).
Traps
- Calling an atypical Spitz nevus melanoma; sentinel node may be needed.
- Missing Muir-Torre when multiple sebaceous tumors appear.
- Overlooking dermatofibrosarcoma protuberans because it mimics a scar.
Rule of thumb
For any pigmented lesion, the histologic report must state Breslow thickness, ulceration, mitotic rate, and margin status; these drive management.
Worked example
A 55-year-old with a pearly nodule and telangiectasia on the nose: biopsy shows basaloid islands with peripheral palisading and clefting; diagnose BCC and treat with excision or Mohs.