Hemorrhage simulating tumor growth in malignant fibrous histiocytoma at MR imaging.

During the course of preoperative chemotherapy for treatment of malignant fibrous histiocytoma of the lower extremity, the mass in three patients was found to be enlarged at physical examination. Magnetic resonance (MR) imaging demonstrated, and subsequent pathologic examination of resected specimens proved, that the enlargement was caused by extensive hemorrhage within the masses, rather than by tumor growth. MR imaging can demonstrate this phenomenon well, particularly on T1-weighted images.