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Updated: Apr 5, 2026
Database-guided Flow-cytometry for Evaluation of Bone Marrow Myeloid Cell Maturation
Published on: November 3, 2018
Morphologically occult systemic mastocytosis in bone marrow: clinicopathologic features and an algorithmic approach
Kaaren K Reichard1, Dong Chen2, Animesh Pardanani3
1From the Divisions of Hematopathology, Reichard.kaaren@mayo.edu.
Objectives:
Bone marrow (BM) biopsy specimens involved by systemic mastocytosis (SM) typically show multifocal, compact, dense aggregates of spindled mast cells (MCs). However, some cases lack aggregate formation and fulfill the World Health Organization 2008 criteria for SM, based on minor criteria.
Methods:
We identified 26 BM cases of KIT D816V-mutated, morphologically occult SM in the BM.
Results:
All patients had some combination of allergic/MC activating symptoms. Peripheral blood counts were generally normal. BM aspirates showed 5% or less MCs, which were only occasionally spindled. BM biopsy specimens showed no morphologic classic MC lesions. Tryptase immunohistochemistry (IHC) demonstrated interstitial, individually distributed MCs (up to 5%) with prominent spindling, lacking aggregate formation. MCs coexpressed CD25 by IHC and/or flow cytometry. Spindled MCs constituted more than 25% of total MCs in all cases and more than 50% in 20 of 26 cases.
Conclusions:
Morphologically occult involvement of normal-appearing BM by SM will be missed without appropriate clinical suspicion and pathologic evaluation by tryptase and CD25 IHC and KIT D816V mutation analysis. On the basis of these findings, we propose a cost-effective, data-driven, evidence-based algorithmic approach to the workup of these cases.
