Cytological features of canine ovarian tumours: a retrospective study of 19 cases

The cytological features of 19 histologically confirmed canine ovarian tumours were retrospectively examined. Seven cases were cytologically classified as papillary adenocarcinoma, eight cases as granulosa cell tumours, two cases as mature ovarian teratomas, one case as a dysgerminoma and one case as a mixed granulosa cell tumour/dysgerminoma. On cytology, papillary adenocarcinoma was characterised by a papillary glandular pattern and tight cohesiveness. Granulosa cell tumours showed monolayered clusters of loosely cohesive granulosa cells. Call-Exner-like bodies were found in five of seven cases. Granulosa cells appeared to be heterogeneous and usually contained several intracytoplasmic vacuoles. Teratoma was characterised cytologically by keratin debris (two cases) and a mixture of epithelial cells with sebaceous, basaloid, columnar/palisading or ciliated appearance (one case). The dysgerminoma contained severely atypical round cells admixed with small lymphocytes. The mixed dysgerminoma/granulosa cell tumour had a mixture of germinal and granulosa cells. Cytological diagnosis was in agreement with histopathology in 18 of 19 (94.7 per cent) cases.