Composite lymphoma of concurrent T zone lymphoma and large cell B cell lymphoma in a dog

摘要

An aspirate of an enlarged popliteal lymph node consists of a predominant population of small lymphocytes that have a moderate amount of pale cytoplasm. At higher magnification frequent cytoplasmic fragments and “hand-mirror” appearance of cells are evident. On histopathology, cortico-medullary distinction of the lymph node is distorted by an expansion of paracortical lymphocytes (bracket). At higher magnification, mitotic figures are absent. With immunohistochemistry, there is faint cytoplasmic and membranous reactivity for CD3 on the neoplastic cells and absent reactivity on a remnant follicle (*), while in reactivity for CD79a is absent on neoplastic cells but prominent on a remnant follicle (*). On flow cytometry, small lymphocytes are uniformly positive for CD5 and MHC II, and negative for CD4, CD8, CD21 and CD45. There is dim detection of CD3. These findings are consistent with TZL