Utility of flow cytometric analysis of mast cells in the diagnosis and classification of adult mastocytosis.

The diagnosis of bone marrow (BM) involvement in mastocytosis has mainly been based on conventional histology. Nevertheless, in recent years, three major methodological advances have been made: the measurement of serum tryptase levels, the immunohistochemical assessment of mast cell (MC) tryptase, and the immunophenotypical characterization of BMMC using flow cytometry (FCM). The most characteristic immunophenotypic feature in mastocytosis is the coexpression of CD2 and CD25 antigens, which are never present in normal BMMC and constitute a phenotypic hallmark of BMMC in adult mastocytosis. Such observations would support the need to include the immunophenotypic analysis of MC in the diagnosis of mastocytosis.