Undifferentiated pleomorphic sarcoma (UPS) is the current name for the sarcoma previously called Malignant Fibrous Histiocytoma (MFH), which are considered the most common type of soft tissue sarcomas.
Undifferentiated pleomorphic sarcoma (UPS) is a soft tissue sarcoma. It used to be called Malignant Fibrous Histiocytoma (MFH). The word “undifferentiated” is used because the cancer cells do not look like the tissue of the body in which they develop. The word “pleomorphic” is used because the cells grow in different sizes and shapes.
UPS is most commonly is found in the legs, arms and sometimes behind the abdominal cavity (retroperitoneum). It is a fast-growing sarcoma that can spread to other parts of the body, most often to the lungs. It usually occurs in older adults. UPS is the most common sarcoma to develop at sites where a patient previously had radiation treatment.
This sarcoma usually presents itself as a painless, enlarging, soft tissue mass. It can grow quite rapidly, at which time the size of the mass can cause pain or a feeling of tight compression. If the mass grows large enough, some patients do present with fever, fatigue and/or weight loss.