Inflammatory myofibroblastic tumor of the urinary bladder diagnosed by anaplastic lymphoma kinase immunostaining.

Inflammatory myofibroblastic tumor (IMFT) of the urinary bladder is an unusual spindle cell lesion that exhibits cytologic atypia, infiltrative growth, and mitotic activity mimicking malignant tumors, such as leiomyosarcoma, rhabdomyosarcoma, and sarcomatoid carcinoma. Recently, anaplastic lymphoma kinase (ALK) gene translocations or ALK protein expression in IMFT has been reported, especially in patients of children and young adults. This lesion has been described in numerous locations in addition to the urinary bladder. The detection of ALK protein and ALK gene rearrangements are useful in distinguishing IMFT from spindle cell malignancies in the urinary bladder.