To investigate ultrasound and MRI features of malignant fibrous histiocytoma (MFH) of soft tissue.Ultrasound, MRI images and pathological data of 12 patients with malignant fibrous histiocytoma in soft tissue confirmed by operation and pathology were analyzed from January 2012 to August 2018, inlcuding 7 males and 5 females, aged from 36 to 69 years old with an average age of 53 years old; the courses of disease ranged from 4 to 49 months with an average of 28 months. Clinical manifestations were soft tissue masses and pain in the affected limbs. Ultrasound, MRI and contrast-enhanced examination were performed before operation. The lesions, morphology, echo/signal characteristics, color flow signals and enhancement features were observed and compared with pathology.In 12 patients with MFH, 9 patients were primary lesions and 3 patients were recurrent lesions after operation. There were 7 cases of bilateral thighs, 2 cases of calves, 1 case of upper arm, 1 case of buttocks and 1 case of posterior peritoneum. The size ranged from 5.1 to 17.1 cm with an average of 8.7 cm. Ultrasound feature showed lobulated or agglomerate, and focused on low echo; 5 cases had capsule and with clear border; 7 cases were unclear boundary with surrounding tissues; and 6 cases with irregular echo-free. The blood flow signals were around the CDFI, and the internal blood flow signals were different. MRI feature showed lobulated, agglomerate or irregular shape, T1WI showed slightly lower signal or equal signal, T2WI showed high signal and DWI signal increased. Six patients manifested mixed signal inside, 7 patients manifested low signal separation inside, 5 patients with false envelope, and 9 patients manifested infiltration and growth with peripheral edema. T1WI showed uneven strengthening after enhancement. Immunohistochemical expression of Vim, CD68 were positive.The age, location and imaging features of soft tissue MFH are characteristic. The diagnosis of MFH should be considered when irregular mass occurred in soft tissues of limbs at middle-aged and old people. Echo and signal are homogeneous or mixed. Separation, necrosis and cystic degeneration could be seen in the mass. When the blood flow signals are abundant and solid components are obviously enhanced, the diagnosis of MFH should be considered.
