Eccrine syringofibroadenoma of clear cell variant: an immunohistochemical study.

Eccrine syringofibroadenoma is a rare eccrine tumor first described by Mascaro in 1963. The clear cell variant was reported by Fretzin in 1995. We describe a hemorrhagic papule on the knee of a 64-year-old woman. Microscopic examination revealed epidermal-based anastomosing thin epithelial cords with ductal structures surrounded by a fibrovascular stroma. Multiple nests of glycogen-containing clear cells were also present. The tumor cells forming the epithelial cords expressed keratin. The eccrine ductal structures and clear cells additionally expressed gross cystic disease fluid protein-15 (GCDFP-15). Reactivity with antibodies against estrogen receptor or progesterone receptor was negative. These results favor the dual differentiation of the clear cell variant of eccrine syringofibroadenoma toward ductal and secretory portions of the eccrine sweat gland.