From the archives of the AFIP: Inflammatory and nonneoplastic bladder masses: radiologic-pathologic correlation.

Although the vast majority of bladder tumors are epithelial neoplasms, a variety of nonneoplastic disorders can cause either focal bladder masses or diffuse mural thickening and mimic malignancy. Some of these entities are rare and poorly understood such as inflammatory pseudotumor, which produces ulcerated, bleeding polypoid bladder masses. These masses may be large and have an extravesical component. Bladder endometriosis manifests as submucosal masses with characteristic magnetic resonance imaging features consisting of hemorrhagic foci and reactive fibrosis. Nephrogenic adenoma has no typical features, and pathologic evaluation is required for diagnosis. Although imaging features of malacoplakia are also nonspecific, characteristic Michaelis-Gutmann bodies are found at pathologic evaluation. The various types of cystitis (cystitis cystica, cystitis glandularis, and eosinophilic cystitis) require pathologic diagnosis. Bladder infection with tuberculosis and schistosomiasis produces nonspecific bladder wall thickening and ulceration in the acute phase and should be suspected in patients who are immunocompromised or from countries where these infections are common. The diagnosis of chemotherapy cystitis and radiation cystitis should be clinically evident, but imaging may be used to determine severity and to assess complications. Extrinsic inflammatory diseases such as Crohn disease and diverticulitis may be associated with fistulas to the bladder and focal bladder wall abnormality. The extravesical findings allow the diagnosis to be made easily. Finally, extrinsic masses arising from the prostate or distal ureter may cause filling defects, which can be confused with intrinsic bladder masses.