Epidemiology of canine cutaneous round cell tumours on the canary archipelago in Spain

In this study we undertook a comprehensive analysis of a Pet Tumour Registry of the Canary Archipelago (PTR-CA) in Spain to investigate the epidemiology of canine cutaneous round cell tumours. From a database of 2526 tumours collected from 2003 to 2020, we conducted a longitudinal analysis of the main trends in diagnosis, age, multiplicity and anatomical distribution as well as a case-control study comparing these cases with the contemporaneous canine population of the Canary Archipelago to analyse breed distribution. In line with former studies, we found histiocytomas mostly affect young dogs (2, IQR 1-5) and mast cell tumours affect middle-to-old dogs (8, IQR 6-10) with grade 1 affecting at younger ages (6.5, IQR 6-8) than both grade 2 (8, IQR 6-10 years) and grade 3 (9, IQR 7-11). Histiocytomas and plasmacytomas showed a similar anatomical distribution appearing mainly on the face, head and neck regions while mast cell tumours occur mainly on limbs and trunk. Higher risk for mast cell tumours and histiocytomas were found for Bulldog-related breeds such as Boxer (OR_MCT  = 23.61, CI95%: 19.12-29.15, OR_HCT  = 10.17, CI95%: 6.60-15.67), Boston Terrier (OR_MCT 19.47, CI95%: 7.73-49.05, OR_HCT 32.61, CI95%: 11.81-90.07) and Pug (OR_MCT 8.10, CI95%: 5.92-11.07, OR_HCT 7.87, CI95%: 4.66-13.28) while Chihuahua dogs showed significantly less risk (OR_MCT 0.18, CI95%: 0.09-0.33, OR_HCT 0.41, CI95%: 0.21-0.78). Notably, the Canarian Mastiff, a local breed, had a low risk of suffering from a mast cell tumour which raises the question of whether this relates to a genetic peculiarity of this breed or some husbandry and environmental factor.