Carcinosarcoma: a primary cutaneous tumor with biphasic differentiation.

We present a case of a primary cutaneous carcinosarcoma (PCS). Histopathologically, PCS is defined as a biphasic tumor composed of malignant epithelial (carcinoma) and mesenchymal (sarcoma) elements. The diagnosis of PCS can be challenging, not only because of its rarity but also because superficial biopsies can result in sampling errors. Accurate diagnosis is essential, as PCS carries a higher recurrence and metastatic rate than epithelial carcinomas, thus requiring wider excision or Mohs micrographic surgery as well as closer clinical follow-up.