NCIt 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.;