Comparison of methods to determine primary tumour size in canine apocrine gland anal sac adenocarcinoma.

Abstract

OBJECTIVES: To assess agreement between measurement of primary apocrine gland anal sac adenocarcinoma tumours using digital palpation, CT and formalin-fixed tissue and to look for associations with metastasis at presentation. MATERIALS AND METHODS: Retrospective study of different methods of measuring primary tumour size in histopathologically-confirmed canine apocrine gland anal sac adenocarcinoma. RESULTS: One hundred sixteen tumours from 107 dogs were included. There was moderate agreement between maximal dimension of the primary tumour measured by CT compared to formalin-fixed tissue and digital palpation. There was no significant difference in median maximum dimension between the measurement methods. Vascular invasion, CT stage, digital rectal examination stage and formalin-fixed tissue stage were significantly associated with metastasis at presentation, while mitotic index of the primary tumour was not. Dogs with tumours >2.5 cm (tumour-stage 2) were significantly more likely to present with metastatic disease. CLINICAL SIGNIFICANCE: In canine apocrine gland anal sac adenocarcinoma, primary tumour size, tumour-stage and vascular invasion are strong predictors of metastasis at presentation.