Presentation
Patient came in asymptomatic with an incidental finding of a urinary bladder mass on routine ultrasound. Cystoscopic evaluation was initially done but showed no intravesical mass. Requested CT urogram for further evaluation.
Patient Data
The urinary bladder is adequately distended with mild circumferential wall thickening. There is a heterogeneously enhancing, well-circumscribed soft tissue mass projecting into the right anterolateral portion of the bladder lumen measuring approximately 4.5 x 3.9 x 4.2 cm (AP x W x CC). Surrounding perivesical stranding densities are seen. Intravesical air locules (from recent instrumentation) and Foley catheter balloon are likewise identified. The prostate gland is enlarged.
There is a slightly enlarged lymph node in the left pelvic sidewall /internal iliac chain. No ascites.
Subcentimeter renal cysts (Bosniak I) are seen. The kidneys are normal in size and contour. No hydronephrosis or opaque lithiasis.
Incidental note of cholelithiases without signs of inflammation as well as small non-inflamed diverticulum in the cecum.
The patient underwent partial cystectomy. Histopathologic report showed a smooth muscle neoplasm, while subsequent immunohistochemical staining showed positive stains for SMA, Desmin, and Caldesmon, supporting the diagnosis of leiomyoma.
Case Discussion
Bladder leiomyomas, although rare (0.43% of bladder tumors), represent the most common non-epithelial / mesenchymal tumor of the urinary bladder. Leiomyomas arise in the submucosa, but growth is most commonly intravesical (as in this case) rather than extravesical. They are smooth, solid, homogeneous masses. Cystic components indicate degeneration. At cystoscopy, the mass may not be evident as normal bladder mucosa may cover the leiomyoma. MR imaging remains superior in demonstrating the submucosal origin of the tumor and the preservation of the muscle layer.
Other urinary bladder masses to be considered include urothelial (transitional) cell carcinoma especially if it exhibits multiplicity, and rarely, leiomyosarcoma (if with necrosis), pheochromocytoma, lymphoma, sarcoma, and metastases.
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