Dogs with malignant tumors exhibit a variable clinical course based on certain tumor and patient characteristics.94 One of the most relevant tumor characteristics regarding prognostication is cellular proliferation.43,94 While most measurement methods of tumor proliferation require immunohistochemistry (such as the Ki67 index) or special stains (such as the AgNOR score), the most practical approach is to measure mitotic activity in routine hematoxylin and eosin–stained tumor sections.142. The gene discussed is MKI67; the disease is neoplasm.