Background: Canine prostatic disease is commonly investigated using cytologic techniques, especially now that ultrasound‐guided fine needle cell aspiration (US‐ENA) is widely available. Few studies, however, have evaluated the diagnostic accuracy of prostatic cytology. Objective: The purpose of this study was to evaluate the usefulness of cytologic investigation of prostatic disease using US‐FNA and other methods in comparison with histopathologic diagnosis.

Methods: Cytologic and histopathologic specimens of prostate or paraprostatic tissue from 25 adult dogs were retrospectively evaluated. Cytologic samples were obtained by US‐FNA, prostatic massage, or direct impression smears or aspirates of tissue at surgery. Histopathologic sections were obtained from tissue collected by biopsy or at necropsy.

Results: Cytologic diagnoses were categorized as nondiagnostic (n = 2); cyst (n = 1); squamous metaplasia (n = 2); inflammation (n = 4); benign prostatic hyperplasia (BPH; n = 5); inflammation and BPH (n = 3); inflammation, BPH, and neoplasia (n = 1); inflammation and neoplasia (n = 3); and neoplasia (n = 4). Cytologic diagnoses agreed with final histologic diagnoses in 20 of the 25 cases (80%). Of those samples collected by US‐FNA, 75% were concordant. Four samples obtained by US‐FNA and 1 sample obtained by prostatic massage and wash had discordant results.

Conclusions: The results of this study suggest strong agreement between cytologic and histopathologic diagnoses for prostatic conditions. Discordance in results obtained by US‐FNA usually was the result of the pathologic process rather than a failure to obtain an appropriate sample.