Cutaneous Metastatic Undifferentiated Pleomorphic Sarcoma from a Mediastinal Sarcoma.

Undifferentiated pleomorphic sarcoma, known as malignant fibrous histiocytoma, is a malignant neoplasm that arises in both soft tissue and bones. In 2002, the World Health Organization declassified malignant fibrous histocytoma as a formal diagnostic entity and renamed it 'undifferentiated pleomorphic sarcoma not otherwise specified.' It most commonly occurs in the lower extremities and rarely metastasizes cutaneously. We report a case of cutaneous metastatic undifferentiated pleomorphic sarcoma of the buttocks occurring in a 73-year-old man diagnosed with mediastinal sarcoma 4 years previously. He first noticed the mass approximately 2 months previously. Histological findings with immunomarkers led to a final diagnosis of cutaneous metastatic sarcoma from mediastinal undifferentiated pleomorphic sarcoma.