Eosinophil, basophil, and mast cell infiltrates in the bone marrow: crossing the boundaries of diagnosis

Abstract

An increase in eosinophils, basophils, and/or mast cells in the bone marrow may pose considerable diagnostic problems for the hematopathologist. In a first step, it is crucial to classify these changes as either being reactive or neoplastic. A slight increase in eosinophils is often seen in reactive states of myeloid hyperplasia while an increase in basophils is usually indicative of a neoplastic hematologic disorder. Regarding mast cells, the presence of compact infiltrates is the major criterion for systemic mastocytosis whereas a diffuse interstitial increase is often encountered in reactive states of mast cell hyperplasia. When a neoplastic disorder is diagnosed, definitive classification depends on immunohistochemical, molecular, and cytogenetic markers. The use of a limited panel of antibodies against basophil-, eosinophil-, and mast cell-related antigens like 2D7, eosinophil major basic protein, tryptase, and CD117 (KIT) is sufficient to identify diffuse or compact infiltrates and to provide semiquantitative analysis of accumulations of neoplastic or reactive cells. We therefore recommend the use of such markers which may increase the value of hematopathologic investigations and thereby are of major help to improve diagnosis and prognostication in these patients.

Eosinophil activation markers in clonal and non-clonal eosinophilia

“…All 4 MDS patients had mature and immature eosinophils in both peripheral blood and bone marrow, an incomplete segmentation of the nucleus in mature eosinophils (pseudo Pelger-Huet anomaly), disproportion of eosinophilic granules, ring shaped nucleus or vacuolated cytoplasm. Peripheral eosinophilia accompanies SM in up to 20 % of cases and bone marrow biopsies often show eosinophilia (4). In our study we included only one patient with smoldering SM, mild peripheral and bone marrow eosinophilia, but no increase in ECP, IL-5 or ECP/Eo ratio.…”

“…Eosinophilia is defined as an abnormal increase of eosinophils in different tissues or in peripheral blood. The degree of eosinophilia can be classified into mild (500 to 1500 cells/µl), moderate (1500 to 5000 cells/µl)) or severe (>5000 cells/µl) (4). An attempt to differentiate the causes of eosinophilia, indicates eosinophilic diseases as clonal or non-clonal (5).…”

Pathogenesis and classification of eosinophil disorders: a review of recent developments in the field

“…Ideally, an immunohistochemical marker panel including CD34, CD117, tryptase and CD25 should be applied [142]. In addition, cytogenetics, FISH and molecular analyses (seeking PDGFRA-, PDGFRB and FGFR1 fusion genes, BCR-ABL, JAK2 V617F, KIT D816V as well as clonal TcR rearrangement) should be performed [23,33].…”