Impact of centralized evaluation of bone marrow histology in systemic mastocytosis

Abstract

BACKGROUND:Bone marrow (BM) histology/immunohistochemistry, KIT D816V mutation analysis and serum tryptase measurements are mandatory tools for diagnosis of systemic mastocytosis (SM).

MATERIALS AND METHODS: Within the 'German Registry of Disorders on Eosinophils and Mast Cells', we identified 65 SM patients who had two consecutive BM biopsies. The first biopsy was evaluated by a local pathologist (LP), the second biopsy by a reference pathologist (RP) of the 'European Competence Network on Mastocytosis (ECNM)'.

RESULTS: Final diagnoses by RP were SM (n = 27), SM or aggressive SM (ASM) with associated non-mast cell lineage hematologic disease [(A)SM-AHNMD, n = 34)] or mast cell leukemia ± AHNMD (n = 4). In 15/65 patients (23%), initial diagnoses by LP were incorrect (by overlooking SM), e.g. primary myelofibrosis (n = 3), myelodysplastic/myeloproliferative neoplasm unclassified (n = 3), B-cell lymphoma (n = 2). Fourteen of 15 patients (93%) with incorrect diagnosis had an advanced SM, mostly (A)SM-AHNMD. In the 50 concordantly diagnosed patients, immunohistochemical markers for quantitative assessment of mast cell infiltration, e.g. CD117 (KIT) or CD25, were applied by LP in only 34/50 patients (68%), and mutational analysis for KIT D816V was performed or recommended in only 13/50 patients (26%). Finally, the subclassification of SM was discordant because LP did not diagnose AHNMD in 9/50 (18%) patients.

CONCLUSIONS: In summary, adequate diagnosis and subclassification of SM requires an in-depth evaluation of the BM by experienced hematopathologists (preferably in a reference center) in combination with molecular genetics, serum tryptase and clinical parameters.

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Identifiers

ORCID for Nicholas C.P. Cross: orcid.org/0000-0001-5481-2555

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