Undifferentiated Soft Tissue Sarcoma

**Semantic type:** Neoplastic Process

**Definition:** A term that refers to a heterogeneous group of uncommon soft tissue sarcomas that do not show an identifiable line of differentiation using currently available technologies. This is a diagnosis of exclusion and includes undifferentiated pleomorphic sarcoma (also known as malignant fibrous histiocytoma), undifferentiated spindle cell sarcoma, undifferentiated round cell sarcoma, and undifferentiated epithelioid sarcoma.

**Synonyms:** - USTS - Undifferentiated Sarcoma - Undifferentiated sarcoma - Undifferentiated/Unclassified Sarcoma - Undifferentiated/Unclassified Soft Tissue Sarcoma