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

• We applied the new Gleason grading to canine prostate carcinomas.
• Most cases obtained the highest Gleason score (GS10).
• As in humans, canine prostate carcinoma has different Gleason-like growth patterns.
• Gleason grading may be potentially applied in the practice settings.

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.