Erythema multiforme and epitheliotropic T-cell lymphoma in the oral cavity of dogs: 1989 to 2009

Objectives: To describe the clinical signs, major laboratory findings, diagnostic procedures and outcome in dogs with erythema multiforme or epitheliotropic T-cell lymphoma of the oral cavity. Methods: Retrospective analysis identified 14 client-owned dogs with erythema multiforme or epitheliotropic T-cell lymphoma of the oral cavity. Histological changes were combined with immunohistochemistry and clonality testing data in selected cases, and a clinical follow-up was acquired. Results: Ulcerative stomatitis with no significant or only minor abnormalities on haematology and serum biochemistry panels was common. Histological features were diagnostic in seven cases. The use of immunohistochemistry distinguished the two diseases in an additional three cases. In four cases, the diagnosis remained questionable, and clonality testing for T-cell receptor gamma gene rearrangement helped confirm erythema multiforme in one case. Clinical follow-up revealed erythema multiforme in two and epitheliotropic T-cell lymphoma in one of the remaining questionable cases. Clinical Significance: Erythema multiforme and epitheliotropic T-cell lymphoma may affect, but are rarely limited to the oral cavity of dogs, and they usually present as stomatitis. Histological features alone are not always diagnostic. Immunohistochemistry and clonality testing may assist in the differentiation between the two, but in ambiguous cases, repeated biopsy and clinical follow-up are essential.