Immunophenotyping of myelodysplasia.

Cell maturation anomalies in bone marrow samples have long been recognized by the patient scrutiny of morphologists, have led to detailed descriptions of possible abnormalities and later to clinically relevant classifications of myelodysplasia (MDS). That the diagnosis and fine description of MDS belong to the realm of morphologists has long been considered a prerogative although, since the early 1980s the development of monoclonal antibodies, progressively allowed maturation-associated immunophenotypic patterns to be defined. The new technology was mostly applied, first in UV microscopy then in flow cytometry, to the definition of acute leukemias with large numbers of identical cells. However, flow cytometrists progressively tried to retrieve the putative maturation stages defined on diseased blasts within normal bone marrow samples. They were thus confronted with the great complexity of the variety of bone marrow cells at various maturation stages physiologically populating our bones, and the need to perfect their skills. As time went by, multicolor labeling and complex gating strategies became increasingly available1 until, at the dawn of the 21st century, it now seems feasible to add immunophenotypic information to the definition of MDS. Such approaches have indeed been recently described,2,3 and one such description is published in this issue of Haematologica.4 Flow cytometry for MDS does, however, jingle some of our well-established routines. Gone are the straightforward evaluations of positive cell percentages. As increasingly suspected with the development of multiparametric labeling, we are here typically in the realm of immunophenotypic patterns, i.e. partly subjective interpretation of the images provided by cytograms built from immunolabeling with lineage and maturity markers. Impressive progress has been made rapidly, but a lot remains to be done, be it only on the proper and pertinent definition of clinically relevant marker associations that can help physicians in decision making.5,6 A new field to watch closely is opening up!