CD30 expression by bone marrow mast cells from different diagnostic variants of systemic mastocytosis

AimsCD30 expression by bone marrow (BM) mast cells (MC) has been reported recently in systemic mastocytosis (SM) patients. The aim of this study was to investigate the potential diagnostic and prognostic value of CD30 expression in SM as assessed by multiparameter flow cytometry. Methods and resultsA total of 163 consecutive BM samples corresponding to 142 SM patients and 21 non-mastocytosis cases were studied. CD30 was positive in most SM patients (80\%), but in only one non-mastocytosis case (4.8\%). When combined with CD25, CD30 contributed to an improved accuracy over that of CD25 alone (98\% versus 93\%) mainly because most (eight of nine) of the well-differentiated SM (WDSM), who lacked CD25, were CD30(+). Similar levels of expression of CD30 were observed among all different subgroups of SM except mast cell leukaemia; among indolent SM (ISM) patients, no significant association was observed between the levels of CD30 expression and other clinical and biological features of the disease. ConclusionsThe increased expression of CD30 associated with absence of CD25 contributes to the diagnosis of WDSM and its distinction from other subtypes of SM. By contrast, CD30 expression did not contribute either to prognostic stratification of ISM or to the differential diagnosis between ISM and aggressive SM cases

Nonaggressive systemic mastocytosis (SM) without skin lesions associated with insect-induced anaphylaxis shows unique features versus other indolent SM

BACKGROUND: Indolent systemic mastocytosis (ISM) without skin lesions (ISMs-) shows a higher prevalence in males, lower serum baseline tryptase levels, and KIT mutation more frequently restricted to bone marrow (BM) mast cells (MCs) than ISM with skin lesions (ISMs+). Interestingly, in almost one-half of ISMs- patients, MC-mediator release episodes are triggered exclusively by insects. OBJECTIVE: We aimed to determine the clinical and laboratory features of ISMs- associated with insect-induced anaphylaxis (insectISMs-) versus other patients with ISM. METHODS: A total of 335 patients presenting with MC activation syndrome, including 143 insectISMs-, 72 ISMs- triggered by other factors (otherISMs-), 56 ISMs+, and 64 nonclonal MC activation syndrome, were studied. RESULTS: Compared with otherISMs- and ISMs+ patients, insectISMs- cases showed marked male predominance (78% vs 53% and 46%; P < .001), a distinct pattern of MC-related symptoms, and significantly lower median serum baseline tryptase levels (22.4 vs 28.7 and 45.8 \u3bcg/L; P 64 .009). Moreover, insectISMs- less frequently presented BM MC aggregates (46% vs 70% and 81%; P 64 .001), and they systematically showed MC-restricted KIT mutation. CONCLUSIONS: ISMs- patients with anaphylaxis triggered exclusively by insects display clinical and laboratory features that are significantly different from other ISM cases, including other ISMs- and ISMs+ patients, suggesting that they represent a unique subgroup of ISM with a particularly low BM MC burden in the absence of adverse prognostic factors