Evaluating mitotic activity in canine and feline solid tumors: Standardizing the parameter

Three different methods for evaluating mitotic activity (mitotic count, mit oses/area, mitotic index) were applied to different types of canine and fel ine solid tumors to determine the method that is most objective and correla tes best with other parameters of cell proliferation. Mitotic activity was evaluated on toluidine blue stained histological sections. Slides stained w ith histochemical (AgNOR proteins) and immunohistochemical (MIB1, PCNA) mar kers of cell proliferation were available for each case. Quantitation of mi totic activity and cell proliferation parameters was performed with an imag e analyzer. Mitotic activity assessment was compared with cell proliferatio n indices and its ability to discriminate tumors grouped on histologically based criteria including the histological type, malignant or benign charact eristics, and grade, A significant correlation by linear regression analysi s with other parameters assessing cell proliferation revealed that mitotic index correlated 100% and mitoses/area and mitotic count correlated 40% of the time. In discriminating the proliferative activity of tumors grouped by histological criteria, mitotic index and mitotic count revealed 100% conco rdance with the other parameters of cell proliferation, while mitoses/areas showed 80% concordance.