Progression of inflammatory myofibroblastic tumor (inflammatory pseudotumor) of soft tissue into sarcoma after several recurrences.

We report a case of inflammatory myofibroblastic tumor (inflammatory pseudotumor) arising in the soft tissue of the right forearm and progressing into frank spindle cell sarcoma after five recurrences and a total span of 12 years. Myofibroblastic nature of the neoplastic spindle cells was shown by electron microscopy and immunohistochemistry. The patient developed multiple pulmonary metastases and died. Although five cases of metastasizing inflammatory myofibroblastic tumors were reported, association of sarcomatous transformation of this entity with metastatic capability was not previously described.