Microcystic adnexal carcinoma

A 55‐year‐old man presented with an ulcer on the right sole present for 8 years. The ulcer measured 6.5 × 3 cm and affected the entire distal sole of the right foot; the margins were everted and an intermittent serosanguineous discharge was present. The general condition of the patient was good, with findings limited to the ulcerated lesion. There was no history of hypertension, diabetes mellitus, or venous stasis. A biopsy taken from the ulcer edge was interpreted as squamous cell carcinoma, Grade I. A transmetatarsal amputation was carried out and the specimen sent for histopathologic examination. Histologically, the epidermis showed ulcerated areas; adjacent areas showed hyperkeratosis and irregular acanthosis. Keratin cysts containing well‐developed lamellar keratin were present in the upper dermis (Fig. 1). Nests and strands of squamous and basaloid cells, having scanty eosinophilic cytoplasm, alternated with the cysts. Areas of ductular differentiation were also noted. The epithelial strands were separated by concentric bands of moderately cellular fibrous tissue in the upper and mid‐dermis. In the deeper areas of the tumor the epithelial nests became progressively smaller in size, diminishing to small clusters of two or three cells, and were surrounded by a sclerotic stroma. Cytologic atypia was minimal and no significant mitotic figures were identified. The neoplasm showed extensive infiltration of subcutaneous fat and striated muscle with frequent perineural involvement in the deeper parts. There was no extension to bone or perichondrium. Immunoperoxidase staining carried out for carcinoembryonic antigen (CEA) showed positivity in the lumina and lining cells of the ducts (Fig. 2). Based upon the classical microscopic appearance, a diagnosis of microcystic adnexal carcinoma was made. The patient has been followed for a period of 3 years with no evidence of tumor recurrence.