Primary Gastric Choriocarcinoma in a Dog

Primary gastric choriocarcinoma (PGC) is a rare neoplasm to date only reported in humans. This report describes a canine gastric tumour with microscopical, histochemical and immunohistochemical features of PGC. The tumour diffusely infiltrated the submucosa and muscularis propria of the pylorus and anterior duodenum, and metastasized to the gastric lymph node. Immunohistochemically, the neoplastic cells displayed aberrant expression of β-catenin and E-cadherin, but normal expression of the adenomatous polyposis coli (APC) protein. Expression of the oncogenes c-myc and Ras was also increased. These observations suggest that this canine PGC had synchronous activation of both the Wnt/β-catenin and Ras signalling pathways of carcinogenesis.