Malignant Fibrous Histiocytoma
Malignant fibrous histiocytoma is a tumor that develops from a primitive mesenchymal cell; it has markers of histiocytoid differentiation. It is the most common malignant neoplasm of soft tissues.
It is seen more often in men, with a peak incidence between 50 and 70 years of age.
Fifty percent are localized in the lower extremities, 20% in the upper extremities, and 20% in the abdominal cavity and retroperitoneum. Other locations are rare.
On MR images, malignant fibrous histiocytoma has low signal intensity with T1 weighting and heterogeneous high signal intensity with T2 weighting. On CT scans, its density is the same as that of muscle and it fi-equently contains areas of lower attenuation that correspond to areas of necrosis.8s MRI is better than CT in determining extent of tumor, but CT is superior in detecting bone involvement and calcifications within the tumor. Calcifications have been seen in up to 20% of malignant fibrous histiocytomas."