Cytology and histopathology have poor to fair agreement for determination of neoplastic or nonneoplastic lesions in dogs with splenic masses or nodules.

Objective: To evaluate the correlation between cytology and histopathology of splenic masses or nodular lesions in dogs. Methods: Retrospective medical record review from January 2014 to July 2022 of dogs that had a splenic mass or nodular lesion and cytologic and histopathologic evaluation within 90 days of each other. Slide review was conducted by a single pathologist from each subspecialty and recorded as neoplastic, possibly neoplastic, or nonneoplastic. Results: 33 dogs were included and had a median of 4 days (range, 0 to 90 days) between cytologic and histopathologic evaluation. Cytologic and histopathologic results agreed in 18 of 33 dogs (55%; 12 nonneoplastic and 6 neoplastic), although the type of neoplasm differed in one of these (sarcoma vs lymphoma). There was disagreement in 8 of 33 dogs (24%; 7 neoplastic on histopathology and nonneoplastic on cytology, 1 nonneoplastic on histopathology and neoplastic on cytology). When including a possibly neoplastic cytologic diagnosis as neoplastic, there was agreement in 22 of 33 dogs (67%) and disagreement in 11 of 33 dogs (33%). In dogs with a neoplastic or possibly neoplastic cytologic diagnosis, 10 of 14 (71%) were neoplastic on histopathology. In dogs with a nonneoplastic cytologic diagnosis, 12 of 19 (63%) were nonneoplastic on histopathology. Conclusions: Cytologic diagnosis correlated with histopathologic diagnosis of splenic masses or nodular lesions in 55% to 67% of dogs. Cytology was accurate in 71% of neoplastic and 63% of nonneoplastic splenic masses or nodular lesions. Clinical Relevance: There is poor to fair agreement between cytology and histopathology in dogs with splenic masses or nodular lesions. A neoplastic cytologic diagnosis more commonly agrees with histopathology than a nonneoplastic diagnosis.