A comparison between the cytological and histological characteristics in thirteen canine and feline thymomas.

Cytological smears and histological sections collected from histologically diagnosed cases of thymoma in nine dogs and four cats were reviewed. Most of the histological features were apparent in the cytological specimens with two notable differences. The epithelial component was underestimated and Hassal's corpuscles were not observed using Wright's-stained cytological preparations. Features of thymoma were recognized in seven of the nine cases in which fine needle aspiration biopsy was done. Therefore, cytology, and specifically fine needle aspiration biopsy, has the potential to be a useful aid in the rapid diagnosis of canine and feline thymomas.