Clear cell syringoid carcinoma - An ultrastructural and immunohistochemical study

Syringoid carcinoma (syringoid "eccrine" carcinoma or eccrine epithelioma) is a rare cutaneous tumor with some controversy regarding its correct defin ition. It may also be difficult to differentiate from its benign counterpar t (syringoma), other adnexal carcinomas, and cutaneous metastasis from aden ocarcinomas. We present a case of a syringoid carcinoma of the clear cell v ariant complemented with an immunohistochemical and ultrastructural study, the latter revealing cytoplasmic accumulation of glycogen and presence of i ntercellular and intracellular lumina in clear tumor cells, as well as dive rse hallmarks of malignancy (i.e., perineural invasion, tumor necrosis, and deep invasion). Clear tumor cells showed cytoplasmic and membranous immuno reactivity to epithelial membrane antigen, carcinoembryonic antigen, kerati ns, and S-100. Our ultrastructural and immunohistochemical results support the ductal differentiation of the glycogen-filled clear cell tumor populati on.