Abstract:

An 84-year-old male presented with multiple painless hyperpigmented patches on his right posterior heel. Five punch biopsies were received from multiple areas. All of the biopsies showed spongiotic dermatitis with lymphocytic exocytosis. The dermal-epidermal junction showed a somewhat “moth-eaten” appearance with perivascular inflammatory infiltrate and numerous melanophages. Three of the biopsies also showed tinea, highlighted by a PAS stain. Given that these were hyperpigmented lesions with melanocytes that were not clearly identifiable on H&E, a Melan-A immunostain was performed and showed focally increased intraepidermal melanocytes in two biopsies with more confluence and irregular pagetoid scatter in one biopsy. Pigment was present irregularly within the stratum corneum. Review of the clinical information revealed a previous history of melanoma at this same site with concern for multiple satellite lesions. The biopsy with the most confluence of melanocytes was diagnosed as consistent with melanoma in-situ. Subsequent excision showed an invasive acral lentiginous melanoma, 6.0 mm in thickness, with features of regression and extension into the subcutaneous tissue. Sentinel lymph node biopsy showed a 1.4 mm metastasis. This case illustrates a potential pitfall of biopsy of the edge of an acral lentiginous melanoma with a spongiotic appearance and concurrent tinea. On acral sites, clinicopathologic correlation is necessary, even when inflammatory or other histopathologic findings are present. If melanocytes are not well visualized on H&E in these cases, immunohistochemistry may help prevent misdiagnosis.

Financial Disclosure:
No current or relevant financial relationships exist.

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Maria Bloomquist, MD