Inflammatory Myofibroblastic Tumors of the Genitourinary Tract—Single Entity or Continuum?

Purpose

Inflammatory myofibroblastic tumor of the genitourinary tract is a spindled soft tissue lesion that is often mistaken for sarcoma. These tumors have been described in numerous sites in the body and have been assigned many names. The relationship between inflammatory myofibroblastic tumor and other morphologically similar entities has been a long-standing source of controversy. We investigated whether inflammatory myofibroblastic tumors in adults and children are the same entity, and whether inflammatory myofibroblastic tumor is part of a biological spectrum that includes benign and malignant entities at opposite ends.

Materials and Methods

We performed an extensive review of the literature.

Results

The literature suggests that with evidence of anaplastic lymphoma kinase rearrangement and expression, the lesion is neoplastic rather than reactive, differentiating it from previously described lesions.

Conclusions

Inflammatory myofibroblastic tumor of the genitourinary tract should be considered a neoplasm of uncertain malignant potential, and routine surveillance and close clinical followup are recommended. Aggressive therapy (radical cystectomy, radiation or chemotherapy) is unwarranted given the indolent and often benign clinical course for the majority of cases. To understand the diagnostic and prognostic implications future emphasis should be placed on the link between genetic abnormalities, and clinical course, therapeutic response and ultimate outcome.

Key Words: urinary bladder, sarcoma, soft tissue neoplasms, immunohistochemistry, carcinosarcoma

Abbreviations and Acronyms: ALK, anaplastic lymphoma kinase, EBV, Epstein Barr virus, FISH, fluorescence in situ hybridization, IMT, inflammatory myofibroblastic tumor, PMP, pseudosarcomatous myofibroblastic proliferation, PSCN, postoperative spindle cell nodule