Immunophenotypic analysis of mast cells in mastocytosis: When and how to do it. Proposals of the Spanish Network on Mastocytosis (REMA).

BACKGROUND: Mastocytosis is a term used for a heterogeneous group of disorders characterized by an abnormal proliferation and accumulation of mast cells (MCs) in one or multiple tissues including skin, bone marrow, liver, spleen, and lymph nodes, among others.
METHODS: In recent years, multiparameter flow cytometric studies have shown that pathologic MCs from patients with mastocytosis display unique aberrant immunophenotypic characteristics as compared with normal MCs.
RESULTS: Among other features, pathologic MCs show aberrant expression of CD25 and CD2 antigens and abnormally high levels of the CD11c and CD35 complement receptors, the CD59 complement regulatory molecule, the CD63 lysosomal membrane antigen, and the CD69 early-activation antigen. In addition, MCs from mastocytosis express abnormally low levels of CD117 and unexpectedly high light scatter and autofluorescence characteristics.
CONCLUSIONS: These aberrant immunophenotypic features are of great relevance for the assessment of tissue involvement in mastocytosis with consequences in the diagnosis, classification, and follow-up of the disease and in its differential diagnosis with other entities. In this paper we provide the reader with information for the objective and reproducible identification of pathologic MCs by using quantitative multiparametric flow cytometry, information for their phenotypic characterization, and the criteria currently used for a correct interpretation of the immunophenotypic results obtained. Copyright 2004 Wiley-Liss, Inc.