Neoplasms of the urinary tract in fish

The veterinary literature contains scattered reports of primary tumors of the urinary tract of fish, dating back to 1906. Many of the more recent reports have been described in association with the Registry of Tumors in Lower Animals, and most of the spontaneous neoplasms of the kidney and urinary bladder are single case reports. In rare instances, such as described in nephroblastomas of Japanese eels and tubular adenomas/adenocarcinomas of Oscars, there is suggestion of a genetic predisposition of certain populations to specific renal neoplasms, environmental carcinogenesis, or potentially an unknown infectious etiology acting as a promoter. Hematopoeitic neoplasms have been infrequently described as primary to the kidney of a variety of fish species, and therefore those case reports of renal lymphoma and plasmacytic leukemia are addressed within the context of this review.