Platynosomum fastosum-induced cholangiocarcinomas in cats

Platynosomum fastosum is a feline biliary tract trematode that generally causes asymptomatic infections. In the early 1980s in Brazil, P. fastosum was associated with cholangiocarcinomas, but this finding was not confirmed in the various publications on the parasite during the last 30 years. This study aims to report three cases of cholangiocarcinomas in cats associated with the presence of P. fastosum. From 2000 to 2011, in the Veterinary Hospital of the Federal University of Campina Grande in northeast Brazil, 348 cats were necropsied, 11 of which (3.16%) were parasitized by P. fastosum. Three cases that resulted in death were associated with cholangiocarcinomas that were found to be associated with P. fastosum. Histologically, the tumors consisted of acini composed of cells with pleomorphic nuclei, loose chromatin, evident nucleoli and lightly eosinophilic cytoplasm. Metastases were observed in two cases. The first case involved metastases to the lungs, kidneys, ovary and peritoneum, and in the second case, the lymph nodes, kidneys, heart and encephalon were involved. The other 8 cats died from other causes, and the parasite was an incidental finding. In those cases, the histologic lesions were nonsuppurative cholangiohepatitis and periductal fibrosis with P. fastosum present. Six animals also showed pre-neoplastic changes (hyperplasia and dysplasia) of the biliary duct epithelium. The study concluded that, as observed in other human biliary tract trematodes, P. fastosum causes cholangiocarcinomas in the liver of cats.