Simple SummaryGastric carcinoma is a type of stomach cancer that occurs more frequently in Tervueren and Groenendael dogs compared to other breeds. In this study, gastric tumour biopsies of 61 Belgian Shepherd dogs were examined for inflammation and tumour location, and subsequently classified using the World Health Organization (WHO) and Laurén classifications, which are commonly used in classifying human gastric carcinoma, as there is no gold standard for the histological evaluation of canine gastric carcinoma as of yet. Survival time after the onset of symptoms was recorded and was investigated in relation to tumour classification. An intestinal type (according to the Laurén classification) and a tubular tumour pattern (according to the WHO classification) were both associated with a longer median survival time. This may aid the practising veterinarian as a prognostic tool for canine gastric carcinoma and provide information regarding the use and reliability of the use of both scoring systems.AbstractGastric carcinoma is generally considered to be a rare disease in dogs, carrying a grave prognosis. However, in the Tervueren and Groenendael varieties of the Belgian Shepherd dog breed, the disease is highly prevalent. While histopathology is the gold standard for diagnosing gastric carcinoma, there is no general consensus on the methods for histological classification in these cases. Biopsies of a group of 61 dogs with confirmed gastric carcinoma (45 Tervueren and 16 Groenendael) were examined and classified according to World Health Organization (WHO) and Laurén classifications. Kaplan–Meier curves were used to compare survival between the different subtypes and simple and multiple linear regression were used to analyse the association between age of onset and breed variant, sex, neuter status, location of the tumour, inflammation score, and Laurén and WHO classifications. Mean age at diagnosis was significantly different in Groenendael (10.1 ± 2.01) and Tervueren dogs (8.5 ± 1.90). The Laurén classification resulted in 29 (48%) diffuse- and 32 (52%) intestinal-type tumours. Applying the WHO classification resulted in 30 (49%) tubular carcinoma growth patterns and 31 (51%) others. Median survival time was significantly reduced for the diffuse type as compared to the intestinal type according to the Laurén classification, with the same median survival time results for tubular compared to non-tubular subtypes according to the WHO classification (median survival time of 61 vs. 182 days, respectively). Using the WHO and Lauren classification on tumour biopsies may help the practising clinician in the prognostication of gastric carcinoma in Tervueren and Groenendael dogs.