COEXPRESSION OF CD79A (JCB117) AND CD3 BY LYMPHOBLASTIC LYMPHOMA

Acute lymphoblastic leukaemia/lymphoma is a malignant disorder derived from the clonal proliferation of lymphoid precursor cells. Whether th e tumour cells are of B- or T-cell type is an important criterion for prognosis which has not been available previously to pathologists, due to the lack of a reliable early B-cell marker functioning an routinel y processed material, This has changed with the production of monoclon al antibodies against the B-cell signalling molecule CD79a, CD79a is e xpressed on normal and neoplastic B cells from the early; stages of B- cell maturation and has been considered to be B-cell-specific, Current ly available antibodies against CD79a, in particular JCB117, allow the identification of B cells, and hence B lymphoblastic disease, in para ffin-embedded material. In this study; the expression of CD79a (JCB117 ) and CD3 has been investigated in 149 cases of T and 68 cases of B ly mphoblastic leukaemia/lymphoma. For the first time, co-expression of C D79a (JCB117) and CD3 is reported in 10 per cent of cases of T lymphob lastic leukaemia/lymphoma. This finding raises questions about the co- expression of T- and B-cell markers in the development of lymphocytes, benign as well as malignant, and alerts pathologists to a potential p roblem in diagnosis, (C) 1998 John Wiley & Sons, Ltd.