Bladder perivascular epithelioid cell neoplasm: Review on clinical features of this rare tumor.

Perivascular epithelioid cell neoplasm (PEComa) is a rare mesenchymal tumor composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. They can arise in various localizations such as the bladder. A total of 36 case reports regarding bladder PEComa have been described in the literature. Eleven reviews regarding this tumor have been published in literature so far primarily focusing on anatomic pathology. Through these reviews, it is known that in bladder PEComa, the melanocytic marker Human Melanoma Black-45 is expressed in 100% of cases whereas variable expression can be seen in multiple other melanocytic and myoid markers such as smooth muscle actin, Melan-A, CD117, S100, CD31, and CD34. Since current reviews mainly emphasize anatomic pathology, we perform a review focusing on the clinical aspects of PEComa at the level of the clinician. A manual electronic search of the PubMed/Medline and Web of Science Core Collection databases was conducted. Search was done on (perivascular epithelioid cell neoplasms [MeSH terms]) AND (Bladder). All case reports and reviews were encompassed until March 15, 2023, to identify studies that assessed bladder PEComa. The age of presentation is relatively low with a median age of 37 years. There is a female predominance with a female/male ratio of 1.5. The tumor shows no preference in anatomical localization within the bladder. Even involvement of the bladder neck, proximal urethra, and distal ureter has been described. The clinical presentation consists in the majority of patients of symptoms related to the urinary tract such as hematuria, dysuria, passage of urine sediment, frequency, and urgency. Other symptoms include abdominal discomfort and dysmenorrhea. In clinical examination, an abdominal mass can be found based on the size and location of the tumor. Further examination usually encompasses cystoscopy due to the hematuria and radiological investigations such as ultrasound (US), computed tomography, and magnetic resonance imaging. These radiological investigations reveal a heterogeneous solid mass with clear borders. In our center, we performed a transvaginal US additionally in a patient with bladder PEComa, which was the only investigation in our patient that concluded the mass was located in the Retzius space. For treatment, transurethral resection of the bladder tumor and partial cystectomy were both described in equal numbers. The choice of treatment depends on the localization and size of the tumor. Follow-up consists of imaging, but clear guidelines on this matter are lacking. Bladder PEComa is a rare condition and usually presents itself with nonspecific symptoms. Radiological investigations will reveal the tumor, but the final diagnosis is based on cytological and immunohistochemical features. Since bladder PEComa is an entity with uncertain malignant potential, it is important to include this entity in the differential diagnosis when a patient presents with lower abdominal discomfort and lower urinary tract symptoms in combination with a mass in the pelvic region.