Basal cell enumeration does not predict malignancy in canine perianal gland tumor cytology

BACKGROUND: Perianal (hepatoid) gland tumors are common in dogs, and the distinction between the benign and malignant forms is clinically important. Cytology of these tumors typically contains many large hepatoid cells and fewer small basal cells. OBJECTIVES: The objective of this study was to determine whether the proportion of the smaller basaloid reserve cells in cytologic samples from perianal tumors correlates with malignancy. METHODS: Eighty-three cases of cytologically diagnosed perianal gland tumors with corresponding histopathologic sections were identified from two separate institutions and included six (7.2%) malignant tumors and 77 (92.8%) benign tumors. The proportion of basal cells from each sample was evaluated. RESULTS: No difference between these groups was found, although the study was sufficiently powered to detect an approximately 1.5-fold change in basal cell proportion. CONCLUSIONS: This report found no evidence that the proportion of basal cells in canine perianal tumor cytology is an indication of the potential for malignancy. We, therefore, do not recommend citing this feature in cytologic reports or when communicating with clinicians.