Diagnostic classification and detection of minimal residual disease (MRD) in canine lymphoma

Abstract

To (i) examine the histopathology and immunophenotype of canine lymphoma according to the NCI Working Formulation and updated Kiel classification adapted to the canine species, (ii) detect clonal rearrangements of antigen receptor genes by PCR assay, (iii) detect Minimal Residual Disease (MRD) in clinical complete remission of chemotherapeutic treated dogs. Fifty formalin-fixed paraffin-embedded tissue from dogs suffering from lymphoma were retrospectively studied. Histopathological results revealed the most common subtype classified by the NCI system was intermediate grade diffuse large cell type (32%) while by the updated Kiel was centroblastic lymphoma(24%).The immunophenotypic study displayed 40% T-subtype (CD3 expression) and 60% B cell (IgM expression) lymphoma. For the PCR assays determining clonality for antigen receptor rearrangement genes and MRD from cytologic and peripheral blood samples of 14 dogs with lymphoma either before chemotherapy and during remission, clonality was detected in 13 of the lymphomas before treatment. MRD was demonstrated in 7 dogs with lymphoma during remission. Detection of MRD during remission in canine lymphoma using PCR technique is considered as an useful tool for prognosis and monitoring relapsing disease.