Microcystic adnexal carcinoma.

We describe a patient with microcystic adnexal carcinoma, a recently recognized cutaneous neoplasm. The patient, a middle-aged woman, had an induration of the left side of her upper lip. At the time of initial resection, the neoplasm also involved the left side of the nose. An extensive recurrence, 27 months later, involved the left turbinates and left orbit. Microscopically the tumor consisted of nests, strands, and cysts composed of mildly to moderately atypical squamous cells that lacked connections with the epidermis. The cysts contained dense, laminated keratin. The tumor was distributed throughout the dermis and infiltrated subcutaneous tissue, skeletal muscle, perichondrium, periosteum, vascular adventitia, and perineural spaces. A few fields contained nests of clear cells, but ductular differentiation, prominent in some microcystic adnexal carcinomas, was not found. There was a distinctive, dense, sclerotic stroma. The foregoing clinical and pathologic findings are characteristic of microcystic adnexal carcinoma. Our observations and available information from the literature suggest the existence of an important family of locally aggressive carcinomas of the face characterized by squamous nests and cysts, variable ductular differentiation, and perineural growth. Such tumors must be clearly differentiated from the more common forms of epidermal and adnexal neoplasia.