Immunophenotyping of low‐grade B‐cell lymphoma in blood and bone marrow: poor correlation between immunophenotype and cytological/histological classification

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Abstract
Results of immunophenotypic examinations of peripheral blood and/or bone marrow (BM), involved in low-grade B-cell non-Hodgkin's lymphomas, were compared with the results of cytomorphological and histopathological examinations in 133 adult patients. 69 cases of chronic B-lymphocytic leukaemia (B-CLL), 16 centrocytic (CC) lymphomas, 14 centroblastic-centrocytic (CB/CC) lymphomas, 15 immunocytomas (IC), 10 cases of hairy cell leukaemia (HCL), four prolymphocytic leukaemias (PLL), two B-CLL in transformation, one splenic lymphoma with villous lymphocytes (SLVL), one hairy cell leukaemia variant (HCL-V), and one lymphocytic lymphoma (LC) were classified according to the Kiel and /or FAB classification. Leukaemic disease was found in 105 cases. The following markers were used for immunocytology (APAAP technique) of blood and/or BM smears: CD 19, CD 5, CD 10, CD 11c, CD 14, CD 21, CD 22, CD 23, CD 25, CD 38 and TdT. All cases tested showed CD 19, but no TdT expression. Every case of HCL had a distinct phenotype with expression of CD 11c, CD 22 and CD 25 and the lack of CD 5 and CD 23 antigens. In all other NHL cases a very heterogenous expression of CD-antigens with no significant correlations to the cytomorphological subtypes was found. The expression of CD 5 is a frequent but inconstant finding in lymphoproliferative diseases other than B-CLL, so 50% of CB/CC, 75% of CC and 80% of IC were CD 5 positive. Our results indicate that, with the exception of HCL, the diagnostic relevance of immunophenotyping for the classification of cytomorphologically and histopathologically defined subtypes in blood and/or BM is of very limited value.