Metastatic genitourinary cancer diagnosed by body fluid cytology: clinicopathologic and cytomorphologic correlation

Malignant effusions secondary to genitourinary cancers constitute less than 5% of metastatic malignancies. Because of their rarity, definitive cytodiagnosis may be challenging. Our study aims to examine the incidence of malignant fluids secondary to genitourinary cancers in our institution, and to characterize their clinicopathologic and cytomorphologic features.

A search of our database was undertaken for all body fluids reviewed from January 2003 through April 2014 at our institution.

During this 11.3-year study period, our search revealed 8255 body fluids. Of these, 1341 (16.2%) were malignant with only 15 (0.2%) due to a genitourinary primary, constituting a mere 1.1% of all malignant fluids. Eight cases (53%) were urothelial carcinomas, 6 (40%) were renal cell carcinomas, and 1 was a bladder leiomyosarcoma (7%). No prostate cancers were found. Seven (47%) involved the pleura, 6 (40%) were in the peritoneum, and 2 (13%) were in the cerebrospinal fluid (CSF). None were detected in the pericardium. Genitourinary metastases comprised 1.9% of peritoneal, 0.8% of pleural, 1.9% of CSF malignant fluids.

Metastatic genitourinary cancers in body fluids are rare, comprising only 0.2% of all fluids and 1.1% of all malignancies. The cytomorphologic features of metastatic urothelial and renal cell carcinoma, although similar to those described in the literature, are nonspecific. To our knowledge, this is the first reported case of metastatic bladder leiomyosarcoma in ascites diagnosed by effusion cytology. Because leiomyosarcoma in body fluids can demonstrate epithelioid features and cohesiveness, it may be confused with metastatic carcinomas.