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 epithelial cells in an organized relationship with stroma. Some of the epithelial cells resemble follicular germ and other cells show follicular sheath differentiation. The neoplasm is symmetrical and well circumscribed. In addition, cytologic examination shows no atypia. Concept of its malignant counterpart is poorly understood. OBJECTIVE We report two trichoblastic neoplasms that show histologic features 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 several 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 showing prominent differentiation towards hair germ and follicular sheath with formation of papillary mesenchymal bodies, follicular bulb-like structures, small keratin cysts and rare malformed hair shaft. The neoplasm showed asymmetry of architecture and massive subcutaneous and muscular infiltration. CONCLUSION With demonstration of these two cases and references of few other reported cases we raise the possibility of existence of trichoblastic carcinoma that is distinct from basal cell carcinoma.