Evaluation of Argyrophilic nucleolar organizer regions (AgNORs) and mitotic index in high and low-grade canine mast cell tumor

The present study was conducted to assess the significance of AgNOR count in different grades of canine mast cell tumor and to investigate its significance with mitotic index. A total of 53 samples of mast cell tumor received in the Department of Veterinary Pathology during a 41-month period (January 2022 to May 2025) were analysed. Grade wise they were divided into high (n=28) and low grade (n=25). Extremities especially legs were the most common site for mast cell tumor. The average AgNOR count and distribution of AgNOR dots were calculated for different grades of tumors. There was significantly higher AgNOR count in high grade mast cell tumor (P=0.003). Mitotic index was significantly more in high grade tumor than low grade (p<0.0001). AgNOR served as a quick, easy and accurate way to assess cell proliferative activity in mast cell tumors.