Epithelioid inflammatory myofibroblastic sarcoma arising in the pleural cavity

A 57-year-old Japanese man presented with massive right pleural effusion, and a huge tumor arising in the pleural cavity was detected by chest computed tomography. A thoracoscopic tumor biopsy revealed that the tumor protruded extensively into the pleural cavity, and its gross appearance was cystic and glossy. Microscopically, the tumor cells were rounded and epithelioid in shape. Prominent and abundant myxoid stroma was also present together with an inflammatory infiltrate, and the tumor was anaplastic lymphoma kinase (ALK)-immunopositive. Fluorescence in situ hybridization revealed that the Ran-binding protein 2-ALK fusion gene was present. Taken together, these findings supported the diagnosis of epithelioid inflammatory myofibroblastic sarcoma (EIMS), which is a variant of an inflammatory myofibrobrastic tumor. This is the first reported case of an EIMS arising in the pleural cavity.