Carcinomatous transformation of eccrine syringofibroadenoma

Background: While squamous cell carcinoma and pseudocarcinomatous hyperplasia have been documented as pre-existing lesions in cases of reactive eccrine syringofibroadenoma (ESFA), to the best of our knowledge carcinoma occurring in a solitary ESFA has not yet been reported. We present one such case in a 91-year-old female who had a dome-shaped, reddish tumor on the extensor side of the left forearm. Methods: We review the histopathological, immunophenotypical and ultrastructural findings of this tumor, including the keratin expression profile. Results: Histopathologically, long, branching, anastomosing, thin and thick strands of small cuboidal epithelial cells were extending from the surface epidermis into the dermis. In the center of the tumor, there were irregular-shaped nests of atypical tumor cells invading downward into the dermis. Ultrastructurally, duct-like lumina lined with cuboidal tumor cells were present in the epithelial cords. From these findings, the present case was diagnosed as solitary eccrine syringofibroadenocarcinoma (ESFAC). Keratin expression studies revealed that cells of the thick strands, except for the luminal and basal cells, were positive for differentiation-specific keratins, keratins 1 and 10, and that cells of the thin strands were positive for keratins 5 and 14. Conclusions: Histopathological, immunophenotypical and ultrastructural evidence, as well as the pattern of keratin expression, suggest differentiation of the present malignant tumor towards the eccrine dermal duct. This case is the first reported case of ESFAC as far as we know.