Immunophenotypic classification of canine malignant lymphoma on formalin-mixed paraffin wax-embedded tissue by means of CD3 and CD79a cell markers.

Canine malignant lymphoma (CML) is a common lymphoid tumour. Identification of the immunophenotype is of prognostic importance: T-cell lymphomas have a worse prognosis than B-cell lymphomas. Until recently, identification of T- or B-cell lymphomas was undertaken by means of flow cytometry or fluorescent immunocytochemistry on frozen sections. Whilst valid in the research field, these methods are impractical for routine diagnostic histopathology in CML. Commercially available CD3 antibody has been successfully employed in T-cell identification in dogs in formalin-fixed paraffin wax-embedded tissue sections, but the lack of a B-cell marker has been a hindrance until the recent introduction of a commercially available pan-B cell marker, CD79a (DAKO M7051), suitable for diagnostic application upon formalin-fixed paraffin wax-embedded material. Antibody markers to CD3 and CD79a show cross-reactivity across species lines for B cells and T cells respectively. In this group of five selected canine cases, two were identified as B-cell and the other three as T-cell lymphoma, by means of CD3 and CD79a. To the best of our knowledge application of CD79a in cases of CML has not been reported.