Eczematous malignant melanoma: a wolf in sheep's clothing.

Background: The clinical diagnosis of amelanotic melanoma is still a challenge.

Case Report: A 72-year-old patient was first referred to us for the excision of a melanoma of the chin. In the first examination, we discovered another melanoma of the trunk. Both malignancies were excised and histopathology confirmed the clinical diagnosis of melanomas with Clark level II and III, respectively. Apart from these melanomas, physical examination revealed an 8 cm x 5 cm large erythematous plaque on the left upper arm. We first thought of a common eczema or a superficial mycosis; a cutaneous T cell lymphoma (CTCL) was considered as well. Surprisingly, the pathology report showed typical features of a malignant melanoma. The diagnosis was confirmed by 3 further punch biopsies (Clark level III, Breslow 0.6 mm). The lesion was excised with 1-cm safety margins.

Conclusions: Amelanotic melanoma may appear as an erythematous macula or plaque; clinical symptoms are erythema, edema, pruritus or a slow increase in size and hypopigmentation or discoloration. Only a biopsy can determine the etiology of a non-specific lesion.