Dear Flow Group We received fresh tissue from a mediastinal mass (female aged 57), teased it into a suspension and typed it by flow. >90% of cells showed a phenotyoe of TdT+ CD1a+ CD2+CC3+ CD4+ CD8+ CD5+ CD7+ with 50% CD10+. This would be consistent with T cell lymphoblastic lymphoma with a cortical thymocyte phenotype. The majority of cells in the cytospin showed the morphology of lymphoblasts.It was noted that the Ki-67 was <1% - unusual for TLL. Immunophenotyping performed on parrafin embedded sections revealed the presence of a population of cells which were Cytokeratin positive and a diagnosis was made of cortical thymoma. The T "blasts" we typed were therefore a background population. Cytokeratin staining on our cytospins showed occasional poorly preserved cells positive. Presumably most of the thymoma cells didn't survive the processing. The question is , what is the significance of CD10 positivity on cortical thymocytes. Is it a normal finding on CD4+CD8+ cells in human thymus? We see it often in T cell ALL and T lymphoblastic lymphoma and initially assumed in this setting that it was suggestive of a maligancy prior to the review of the histology. Thanks Jan Jan Nelson Molecular Haematology Department of Molecular Medicine The University of Auckland Phone: (+64)(9) 373-7599 ext 6381 Fax: (+64)(9) 373-7292
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