Primary Cutaneous Carcinosarcoma: Report of a Case with Poroid and Fibrohistiocytic Differentiation.

Primary cutaneous carcinosarcoma is an infrequent cutaneous biphasic tumor composed of an epithelial and a mesenchymal component, both with malignant features. The epithelial component frequently shows squamoid or basaloid differentiation but other differentiations, such as adnexal, have also been described. The mesenchymal component shows diverse cellular lineages such as smooth muscle, nervous, osteoblastic, chondroblastic, myofibroblastic, angiomatous, and fibrosarcomatous among others. Local recurrences with low metastatic potential are also reported. We present the case of an 89-year-old man with an exophytic tumor located in the back of the left leg. The biopsy showed a cutaneous carcinosarcoma with adnexal differentiation (porocarcinoma) and pleomorphic sarcoma with fibrohistiocytic differentiation.