Trichoblastic carcinoma: A report of two cases of a deeply infiltrative trichoblastic neoplasm

BACKGROUND Trichoblastoma is a benign neoplasm with primitive hair follicle differentiation. The tumor is characterized by nests and cords of epitheli al cells in an organized relationship with stroma. Some of the epithelial c ells resemble follicular germ and other cells show follicular sheath differ entiation. The neoplasm is symmetrical and well circumscribed. In addition, cytologic examination shows no atypia. Concept of its malignant counterpar t is poorly understood. OBJECTIVE We report two trichoblastic neoplasms that show histologic featur es of malignancy. METHODS Skin biopsies from the lip region of a 53-year-old female and a 74- year-old male who had presented with the neoplasms in that location for sev eral years were reviewed. Excised specimens measured 2 x 1 x 1 cm and 1.6 x 0.7 x 0.8 cm respectively. RESULTS The histologic sections revealed locally aggressive neoplasms showi ng prominent differentiation towards hair germ and follicular sheath with f ormation of papillary mesenchymal bodies, follicular bulb-like structures, small keratin cysts and rare malformed hair shaft. The neoplasm showed asym metry of architecture and massive subcutaneous and muscular infiltration. CONCLUSION With demonstration of these two cases and references of few othe r reported cases we raise the possibility of existence of trichoblastic car cinoma that is distinct from basal cell carcinoma.