The prognostic significance of AgNOR counts and PCNA-positive cell counts in canine malignant lymphomas

The behaviour of canine malignant lymphomas is difficult to predict on the basis of histomorphology alone, but the majority of such tumours are "high-grade" by most classifications. The aim of this study was to examine the prognostic significance of argyrophilic nucleolar organizer region (AgNOR) counts and of proliferating cell nuclear antigen (PCNA)-positive cell counts in canine malignant lymphomas; and to relate the results to the histological grade (Kiel classification) and to the survival time of treated and untreated dogs. Low- and high-grade malignant lymphomas differed significantly in having mean AgNOR counts of 3.3 and 5.7 respectively. Untreated dogs with a mean AgNOR count higher than 5.5 did not survive more than 85 days; the median survival time for this group was 38.5 days. Untreated dogs with a mean AgNOR count lower than 4.0 survived at least 82 days and one dog more than 300 days; the median survival time for this group was 154 days. Treated dogs with a mean AgNOR count higher than 5.5 did not survive more than 126 days; the median survival time for this group was 73.5 days. Treated dogs with a mean AgNOR count lower than 4.0 had a median survival time of 205.5 days and one dog survived 367 days. The mean AgNOR count would seem to be a valuable prognostic marker for canine malignant lymphomas, but PCNA counts had no prognostic significance in relation to the median survival time in treated or untreated dogs.