Eccrine porocarcinoma with Bowenoid changes: epithelial membrane antigen is not a useful marker for malignant tumours arising from eccrine gland structures.

A case of eccrine porocarcinoma with Bowenoid changes is reported. We compared the results of immunohistochemical staining for epithelial membrane antigen in the present case with results in Bowen's disease to determine whether the presence of epithelial membrane antigen (EMA) enabled us to differentiate between Bowen's disease and eccrine porocarcinoma with Bowenoid changes. Histologically, the present tumour was characterized by atypical clear cells with Bowenoid changes as well as uniform small cells and intradermal nests with ductal structures. The membrane and cytoplasm of uniform small cells and ductal luminal surfaces were positive for EMA. However, the atypical cells with Bowenoid changes were negative for this. In contrast, tumour cells in Bowen's disease were positive for EMA. Although EMA is known to be a useful marker for some benign tumours derived from eccrine ducts, we found it difficult to distinguish eccrine porocarcinoma with Bowenoid changes from Bowen's disease using immunohistochemical staining for EMA.