Immunophenotypic and cytomorphologic subclassification of T-cell lymphoma in the boxer breed

The boxer breed is at high risk for developing lymphoma and, in contrast to the general canine population, is predisposed to the T-cell variant of the disease. The purpose of this study was to more accurately classify lymphoma in this breed. Clinical, cytomorphologic and immunophenotypic data were examined in 43 boxers with lymphoma. Twenty-five cases were collected prospectively and a further 18 cases were obtained retrospectively. Lymphomas were classified as multicentric (n = 29), mediastinal (n = 6) and intestinal (n = 8). Of the 40 immunophenotyped samples, 34 (85%) were T-cell, 5 (12.5%) were B-cell and 1 was a non-B-cell non-T-cell lymphoma. Immunophenotypic subtyping was done on prospectively collected T-cell lymphoma samples (n = 22) to differentiate CD4 (helper) from CD8 (cytotoxic) T-cell origin as well as to determine the T-cell receptor (TCR) expression (TCRαβ vs. TCRδγ). Phenotypic expression was CD4+ (n = 12), double negative (DN) (n = 6), double positive (DP) (n = 1) and CD8+ (n = 1), respectively, while two samples had no interpretable result. 20/22 samples were TCRαβ+ with only 1 sample being TCRδγ+ and 1 with no interpretable result. Cytomorphologic analysis was done on the same 22 samples using the World Health Organization (WHO) classification scheme. According to this scheme, 17/22 samples were classified as lymphoblastic, 2/22 as large cell peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS), 2/22 as large granular lymphoma (LGL) high-grade and 1/22 as small lymphocytic. The results of this study indicate that lymphoma in the boxer breed is a disease comprised predominantly of TCRαβ+, CD4+ (helper) T-cells with lymphoblastic (high-grade) morphology.