[Malignant melanoma with pseudoepitheliomatous reaction marker. A case report].

Pseudoepitheliomatous hyperplasia or pseudocarcinomatous hyperplasia (PEH) is characterized by a downward expansion of the epidermis, which can simulate a squamous cell carcinoma (SC). It is usually associated to chronic inflammatory conditions, but rarely it can hide a tumour. In the present paper a case of melanoma (M) associated with a prominent PEH is described. The patient is a 79-year old woman who presented a polypoid, ulcerated lesion of the left thigh. The lesion was entirely removed. The patient is free of disease 5-years after surgery. On histology, the malignant melanomatous proliferation was closely admixed to sheets of squamous cells. The possibility of SC was excluded as the squamous component did not show architectural disarray, prominent nucleoli and atypical mitoses. Siringomatous metaplasia was observed in the deeper portion of the lesion. On the basis of these findings the diagnosis of melanoma (M) associated to prominent PEH was considered the most likely.