Age / Sex : 69 / F

Age / Sex :  69/F

proliferative myositis

Discussion

Findings:

On initial MRI,

About 2.7 x 2.5 x 5.2cm sized, T1 mild hyperintense and T2 hyperintense mass in vastus lateralis, with good enhancement   

On FU MRI,

Focal area of subtle high signal intensity on T1 and T2WI with mild enhancement at vastus lateralis, right.

 - with linear low signal intensity at subcutaneous fat on T1 and T2WI.

 - site of mass on previous outside MRI.

 --> postop change, more likely.

Differential Diagnosis:

malignant soft tissue tumor, such as

MFH, liposarcoma (possibly pleomorphic or myxoid type), leiomyosarcoma, synovial sarcoma.

Diagnosis:  Proliferative Myositis

Discussion: Proliferative Myositis

Pseudosarcomatous proliferative soft tissue lesion

Common in Adults ( mean age 50 yrs )

Location : Head and neck , Upper Extremities

Histolopathology : Infiltration with basophilic giant cells and proliferative fibroblast

Clinical finding : rapidly enlarging solitary soft tissue mass, firm and painful

Differentials : soft-tissue tumors (angiomatous lesions, lipoma, MFH, sarcomas), traumatic injury, myositis ossificans, muscle sarcoidosis, etc.

Treatment : Local excision or Observation

References:

Radiology 2007 ; 244 : 613 - 616

Radiographics 2004  24 : 1477-1481