A Retrospective Evaluation of Oral Lymphoma in 75 Dogs (2019-2022): Clinical and Histopathological Features

Canine oral lymphoma is an uncommon neoplasm that mimics inflammatory or immune-mediated oral diseases as well as other round-cell tumors, complicating diagnosis and potentially delaying treatment. The objective of this study was to describe the clinical presentation, behavior, and outcomes of canines diagnosed with oral lymphoma, including epitheliotropic and nonepitheliotropic forms of the disease. A retrospective review of 75 cases diagnosed between 2019 and 2022 was performed, evaluating histologic categorization, lesion characteristics (solitary vs multifocal, anatomic location, and descriptors), and survival data when obtainable. There were 73 cases (97.3%) of epitheliotropic T-cell lymphoma (ETCL), 1 case (1.3%) of lingual T-zone lymphoma, and 1 case (1.3%) of peripheral T cell lymphoma-not otherwise specified. The most common anatomic locations for ETCL were the mucocutaneous junction (65.3%) and buccal or labial mucosa (62.7%). Lesions affecting the mucocutaneous junction were commonly located on the mandibular labial frenulum (61.2%), and 46.7% of mandibular frenulum lesions were the only lesions present in the oral cavity. Lesions associated with ETCL were likely to be multifocal (57.3%) and ulcerated (62.8%). Patient survival was not significantly associated with lesion number (solitary vs multifocal) among epitheliotropic cases. These findings indicate that canine oral lymphoma is predominantly epitheliotropic and frequently multifocal, underscoring the importance of biopsy and histopathologic evaluation of oral tissues exhibiting subtle mucosal changes such as erythema or depigmentation. Adjunctive diagnostics, including immunohistochemistry, flow cytometry, and polymerase chain reaction for antigen receptor rearrangements, may facilitate earlier detection. Prospective studies are warranted to clarify disease progression, treatment response, and prognosis.