Primary role of multiparametric flow cytometry in the diagnostic work‐up of indolent clonal mast cell disorders

Abstract

Background: According to the World Health Organization (WHO) classification the diagnosis of systemic mastocytosis (SM) relies on bone marrow (BM) examination and is based on one major and four minor criteria. Herein, we used WHO criteria to compare flow cytometry (FC) with other available techniques in the diagnosis of SM after BM examination.Methods: We analyzed a cohort of 95 patients with suspect SM. All patients underwent comprehensive BM examination by using cytology, immunohistochemistry, FC and molecular study for mutation of c-Kit and serum tryptase dosage. FC evaluation was based on a combination of monoclonal antibodies, specifically CD25/CD2/CD45/CD34/CD117.Results: Seventy-four out of ninety-five patients were diagnosed with indolent SM (n 5 59) or monoclonal mast cell activation syndrome (n 5 15) because satisfying less than 3 minor criteria. Thirty-nine out of these seventy-four patients fulfilled the major histological criterion, whereas the presence of a minor criterion was assessed by FC, molecular study, cytology, and tryptase level in 70/74, 52/67, 56/ 74, and 42/74 patients, respectively. FC showed higher sensitivity than IHC in detection of CD251 mast cells (MC) (92.9% vs. 73.8%; P 5 0.019), especially in the absence of the major histological criterion (90.5% vs. 47.6%; P 5 0.003). Moreover, CD2 expression was documented by FC and IHC in 97.1% and 35.3% of cases, respectively (P < 0.001).Conclusions: FC showed the best sensitivity for identifying abnormal MC compared to other techniques, especially in cases with low MC burden. Therefore, we hope for a major role of FC in the diagnostic work-up of clonal MC disorders. V C 2011 International Clinical Cytometry Society

Mast Cells in Systemic Mastocytosis Have Distinctly Brighter CD45 Expression by Flow Cytometry

“…5 Yet, more recently, CD45 has been reported to be significantly brighter in cases of clonal mast cell disease than in cases with cutaneous mastocytosis and cases without mastocytosis. 15 Teodosio et al 16 found CD45 to be significantly brighter in cases of SM compared with normal bone marrow specimens. More specifically, the cases of clonal mast cell activation disorder and indolent SM had significantly brighter CD45 expression, while cases of well-differentiated SM, indolent SM associated with a clonal non-mast cell lineage hematopoietic disease (ISM-AHNDM), aggressive SM (ASM), ASM-AHNMD, and mast cell leukemia had CD45 expression not significantly different from controls.…”

“…23 Flow cytometry has been reported to have higher sensitivity than immunohistochemistry for detecting abnormal mast cells. 15 However, and interestingly, the percentage of mast cells detected by flow cytometry is quite low. In our study, mast cells were lower by a factor of 3 to 250 by flow cytometry compared with bone marrow morphology/biopsy (Table 1), similar to previous studies.…”

“…However, it has previously been reported that the major criterion for the diagnosis of SM may not always be identified (identified in 67%-68% of cases). 14,15 As such, ancillary testing, including immunophenotyping and molecular studies, is necessary for the diagnosis. In this study, we found that the flow cytometry finding of bright CD45 expression, together with CD25 expression on mast cells, identified cases of SM with a specificity of 100%.…”

“…Increased autofluorescence has been described to be especially evident in the FITC channel (~525 nm), which overlaps with emission spectra of naturally occurring cytoplasmic molecules within mast cells. 7,18,19 While autofluorescence was considered as a potentially significant source of the increased CD45 expression, PerCP (emission maximum of ~675 nm) was coupled with CD45, a fluorophore pairing employed by ourselves and others, 15,16 to reduce the contribution of autofluorescence of mast cells. In addition, PerCP isotype controls did not show a numerically significant enough contribution of autofluorescence of mast cells in this channel to affect comparison of SM and non-SM mast cells.…”

Bone marrow tryptase as a possible diagnostic criterion for adult systemic mastocytosis

“…Their diagnostic properties have not been fully established [3,11,[30][31][32][33][34][35]. Their diagnostic properties have not been fully established [3,11,[30][31][32][33][34][35].…”