Fine needle aspiration cytology: high accuracy in diagnosing cutaneous and subcutaneous neoplasms in dogs

The fine-needle aspiration cytology (FNAC) is a widely used technique for the screening and diagnosis of cutaneous and subcutaneous masses in dogs. In our laboratory routine, FNAC has been performed since 2008, and increasing demand is evident. However, until now, no studies have been performed using these samples. This study aimed to establish the diagnostic agreement between FNAC, and histopathology performed in cutaneous and subcutaneous masses from dogs. FNAC samples collected from cutaneous and subcutaneous masses on dogs between January 2017 and May 2019, archived in the Veterinary Clinical Laboratory (VCL-UFSM), which also had respective histopathologic results, were included. A clinical pathologist with 3 years of experience reviewed the cytologic specimens. The cytologic diagnosis was compared to the histopathologic diagnosis, used as the gold standard technique, to determine FNAC accuracy in diagnosing neoplasia as well as the sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV). Eighty cytologic samples were included. Sixty-seven samples were neoplastic (65 true positives and 2 false positives), and 13 samples were non-neoplastic (9 true negatives and 4 false negatives). The accuracy of FNAC for diagnosing cutaneous and subcutaneous neoplasms was 93% (74/80), with a Se of 94.3% (65/69), Sp of 81.8% (9/10), PPV of 97% (65/67), and NPV of 69.2% (9/13). This study demonstrates that FNAC is an excellent diagnostic tool for diagnosing cutaneous and subcutaneous neoplasms in dogs and should always be performed as available in the veterinary clinic routine.