Epidermotropic Bullous and Erosive Metastatic Melanoma
Woltsche et al1 have recently reviewed bullous melanoma in this journal. Altogether, 13 cases have been described so far in the literature.1 Most of the cases have been found to be bullous histopathologically, whereas a few cases have also demonstrated bullae clinically.2–5 There was 1 reported case of bullous metastatic melanoma.6 The bullae have been described histopathologically to be intraepidermal or subepidermal.1 Herein, we describe an unusual case of epidermotropic metastatic melanoma showing erosions clinically and bullae histopathologically, both subepidermal and intraepidermal.
A 64-year-old woman who emigrated from Ethiopia 4 years before was referred to our clinic for edema and erosions on her right foot for 6 months. She had tuberculosis 4 years ago, which was treated by rifampicin. The physical examination revealed numerous hyperpigmented papules and nodules on the right calf and on the medial aspect of the right ankle (Fig. 1A). The right foot was edematous with numerous large erosions on the anterior plantar skin and on the medial side of the foot, surrounded by hyperpigmention (Figs. 1B, C). The biopsy from an edge of a plantar ulcer demonstrated complete dermoepidermal separation (blister) with numerous melanoma cells in the separation space and in the underlying dermis along numerous melanophages (Figs. 2A–C). The biopsy from a nodule on the right medial ankle showed marked epidermal hyperplasia with numerous melanoma cells in the papillary dermis and in the epidermis mostly in the basal cell layer as in epidermotropic melanoma. The biopsy of a papule in the right upper calf demonstrated epidermotropic melanoma cells forming an intraepidermal blister (Fig. 2D). The primary tumor could not be identified with certainty although the planter erosive hyperpigmented skin was the main suspect. Analysis for BRAF mutation was negative, and imaging did not show extensions beyond the skin.
Histopathologically, the “acantholytic” pattern seems to be the most common presentation of bullous melanoma, mimicking pemphigus vulgaris or Hailey–Hailey disease.1 In our case, the blisters formed either subepidermally (Figs. 1A–C) or intraepidermally (Fig d), indicating that both types of blisters may be seen in a single patient with bullous melanoma. Blistering in primary and metastatic melanoma is considered to be rare both clinically and histopathologically, but melanoma should be considered in the differential diagnosis of erosive and blistering skin diseases.