Lesion distribution based on oral biopsy and histopathology in dogs: a retrospective study of 338 cases (2015-2025).

The histopathologic spectrum of canine oral lesions can vary significantly by geographic region and breed demographics. This retrospective study aimed to characterize the distribution of 338 biopsy-confirmed canine oral masses in the Republic of Korea, where small-breed dogs predominate. Lesions were categorized into tumor-like, benign, and malignant groups. Clinicopathologic features and anatomical distributions were compared. Tumor-like (non-neoplastic) lesions accounted for 52.7% of all cases. Among the 160 confirmed neoplasms, benign tumors (73.7%) were more frequent than malignant tumors (26.3%). Peripheral odontogenic fibroma (POF) and canine acanthomatous ameloblastoma (CAA) were the predominant benign tumors. Notably, squamous cell carcinoma (SCC) was the most frequently identified malignant tumor (50.0%), followed by malignant melanoma (MM) (26.2%). This contrasts with several large-scale studies from other countries where MM typically predominates. Dogs with malignant tumors were significantly older (median 12.0 years) than those with benign tumors (median 9.0 years). Body weight, gender, and overall anatomical distribution showed no significant association with malignancy, although specific tumors exhibited distinct site preferences. The high proportion of non-neoplastic lesions among biopsy-confirmed cases emphasizes that clinically apparent oral masses require histopathologic confirmation. Furthermore, awareness of age-related risks and site-specific tumor distribution patterns can assist clinicians in prioritizing differential diagnoses during clinical evaluation.