Phenotypical characterization and clinical outcome of canine Burkitt-like lymphoma

In dogs, Burkitt-like lymphoma (B-LL) is rare tumor and it isclassified as a high-gradeB-cell malignancy. The diagnosis is challenging because ofthe similar histologicappearance with other histotypes, no defined phenotypical criteria and poorly describedclinical aspects. The aim of the study was to provide a detailed description ofclinical and morphological features, as well as immunophenotypical profile of B-LLin comparison with the human counterpart. Thirteen dogs with histologically provenB-LL, for which a complete staging and follow-up were available, were retrospectivelyselected. Immunohistochemical expression of CD20, PAX5, CD3, CD10, BCL2, BCL6,MYC, and caspase-3 was evaluated. Histologically, all B-LLs showed a diffusearchitecture with medium to large-sized cells, high mitotic rate and diffuse starry skyappearance. B-phenotype of neoplastic cells was confirmed both by flow-cytometry andimmunohistochemistry. Conversely, B-LLs were negative for BCL2 and MYC, whereassome cases co-expressed BCL6 and CD10, suggesting a germinal center B-cell origin.Disease stage was advanced in the majority of cases. All dogsreceived CHOP-basedchemotherapy with or without immunotherapy. Despite treatment, prognosis was poor,with a median time to progression and survival of 130 and 228 days, respectively.Nevertheless,∼30% of dogs survived more than 1 year. An increased apoptoticindex, ahigh turnover index and caspase-3 index correlated with shorter survival. In conclusion,canine B-LL shows phenotypical differences with the human counterpart along withfeatures that might help to differentiate this entity from diffuse large B-cell lymphoma