Localized amyloidosis of the prostatic urethra mimicking urothelial carcinoma

Abstract

Amyloidosis is a disease characterized by extracellular deposition of amyloid protein fibrils in tissues. It rarely involves the urethra with just over 50 cases reported in the English language literature. We report a case of urethral amyloidosis that mimicked urothelial carcinoma clinically. The patient is a 69-year-old male who presented to the emergency department with shortness of breath. An abdominal CT scan demonstrated a right hydronephrotic kidney and a large, predominantly hyperdense lesion, presumed to be hematoma largely occupying the urinary bladder. Pan-cystoscopy revealed a 6 cm bladder mass involving the prostatic urethra displacing the right ureteral orifice, which was biopsied. Histologic examination showed numerous osteoclast-type giant cells, with areas of extensive calcification and multifocal ossification interspaced by large deposits of amorphous eosinophilic material. Amyloid deposition was confirmed by Congo red and sulfated Alcian blue stains. Light chromatography tandem mass spectrometry was performed and detected multiple types of proteins including serum amyloid P component, apolipoprotein A4, and apolipoprotein E; however, a dominant amyloid type was not identified. The patient had no history of infection or localized inflammation. Further investigations for systemic amyloidosis were all negative. Amyloidosis of the urethra is extremely rare and may either be localized, idiopathic or a manifestation of systemic amyloidosis. Physicians among various specialties, including urologists, pathologists and radiologists should be aware of this rare entity, as this lesion may be easily mistaken for malignancy further emphasizing the importance of tissue diagnosis before definitive surgery. Long-term follow-up in the absence of symptoms may not be required.