Proposal of Gleason-like grading system of canine prostate carcinoma in veterinary pathology practice

Gleason grading - the most useful predictor of prognosis for prostate cancer in men - was updated at a 2005 consensus conference by the International Society of Urological Pathology. Since Gleason-like growth patterns have been recognised in dogs, this study aimed to apply the modified Gleason grading to 45 canine prostate carcinomas. A single primary growth pattern was observed in 28 cases, a secondary pattern in 11 cases and a tertiary pattern in 6 cases. Cribriform, solid and small acinar/ductal were the most common primary, secondary and tertiary morphological patterns, respectively. The highest Gleason score (GS10) was obtained in 46.7% of cases. Nine of 14 metastasizing cases were classified as GS10. Gleason pattern 5 was present in 33 of cases. This study suggests that the modified Gleason grading, based on specific histological growth patterns existing in canine prostate carcinomas, may be accepted as a grading system for histopathology in the practice settings in order to complete the clinical assessment for the best management of the patient.