Trichoblastic carcinosarcoma: an authentic cutaneous carcinosarcoma

Abstract

We describe a trichoblastic carcinosarcoma on the forehead of a 65-year-old man. This is the fifth case of trichoblastic carcinosarcoma in the literature and the first to be reported from the USA. It was successfully treated with direct excision. Trichoblastic carcinosarcoma should be distinguished from epidermal carcinosarcoma. We believe trichoblastic carcinosarcoma is an authentic carcinosarcoma derived from multiple progenitor cells whereas epidermal carcinosarcomas are derived from a single progenitor cell that undergoes epithelial to mesenchymal transition, and are better considered as sarcomatoid carcinomas.

Figure 1

(A) Scanning magnification demonstrates a biphasic skin tumour (H&E, ×20). (B) The tumour is comprised of a circumscribed nodule of basophilic follicular germinative cells surrounded by spindled cells in an eosinophilic fibroinflammatory matrix (H&E, ×100). (C) The follicular germinative cells exhibit focal crowding and aberrant mitotic activity (H&E, ×400). (D) The spindled cells exhibit pleomorphism and infiltrative growth pattern around an eccrine gland (H&E, ×400).

Figure 2

(A) The follicular germinative cells express high-molecular weight keratin (34βE-12, ×400). (B) The trichogenic specific stroma around the follicular germinative cells is weakly positive for CD10; the pleomorphic spindled cells are strongly positive for CD10 (CD10, ×400).