Cutaneous clear cell tumors can pose a diagnostic challenge even to the experienced dermatopathologist; this is partly because of limitations of existing diagnostic categories.
To describe a previously unrecognized, distinctive cutaneous adnexal carcinoma capable of an aggressive clinical course.
Clinicopathologic analysis of a series of 12 cases.
The patients were older individuals (median age, 71 years) with equal gender frequency. The lesions showed wide anatomic distribution with predilection for the head and neck area, especially the scalp. The lesions presented as rapidly growing, erythematous to flesh-colored, solitary papules/nodules that were capable of quickly reaching a size of several centimeters. Histologically, adnexal clear cell carcinoma with comedonecrosis was characterized by dermal proliferation of nests of epithelial cells showing distinctive zonal arrangement. The periphery of the tumor nests was formed by squamoid cells merging with centrally located clear cell areas containing foci of comedonecrosis. The lesions often showed multilobular or trabecular growth pattern and infiltrating border. Nuclear pleomorphism was variable; mitotic count ranged from 2 to 32/mm2 (median, 8/mm2). No ductal, cuticular, or apocrine differentiation was seen. All cases showed expression of epithelial membrane antigen and cytokeratin 17 in clear cells, with focal carcinoembryonic antigen expression in some cases. Follow-up (average, 37 months) revealed local recurrence (4 cases) and regional and distant metastases (2 cases).
Adnexal clear cell carcinoma with comedonecrosis appears to be a distinctive adnexal neoplasm that has to be distinguished from more indolent squamous cell and tricholemmal carcinomas.