Immunophenotype of bone marrow mast cells in indolent systemic mast cell disease in adults

One of the major advances in the histological diagnosis of bone marrow (BM) involvement in mastocytosis has been the specific immunohistochemical dete ction of tryptase on most cells (MC), which has shown to be of great diagno stic value, especially in cases of malignant mastocytosis. On the other han d, recent studies have clearly shown that bone marrow mast cells can be spe cifically identified and accurately enumerated using multiparametric flow c ytometry, which allow a systematic analysis of the immunophenotypic charact eristics of bone marrow mast cells. Once this flow cytometric approach was applied for the analysis of BMMC from mastocytosis patients clear immunophe notypical differences were found between BMMC from normal individuals and a dults with mastocytosis, The most characteristic immunophenotypic feature, both in malignant and adult indolent systemic mast cell disease, being the coexpression of CD2 and CD25 antigens, never present in normal bone marrow mast cells and, which constitute an aberrant hallmark of bone marrow mart c ells in adult mastocytosis. Furthermore, bone mast cells from mastocytosis display a higher reactivity for CD35, CD63, and CD69 activation-associated antigens. Based on these results it could be concluded that the use of mult iparametric flow cytometric immunophenotyping of BMMC in adult patients suf fering from cutaneous mastocytosis can be of great utility for the diagnosi s of BM involvement; additionally, this might also help to establish the re al incidence of BM involvement in cutaneous mastocytosis.