J Clin Pathol 57:604-608 doi:10.1136/jcp.2003.014860
  • Original article

Systemic mastocytosis with associated clonal haematological non-mast cell lineage diseases: a histopathological challenge

  1. H-P Horny1,
  2. K Sotlar2,
  3. W R Sperr3,
  4. P Valent3
  1. 1Institute of Pathology, University of Lübeck, D-23538 Lübeck, Germany
  2. 2Institute of Pathology, University of Tübingen, D-72076 Tübingen, Germany
  3. 3University of Vienna, AKH, Department of Internal Medicine/Division of Haematology and Haemostaseology, A-1090 Vienna, Austria
  1. Correspondence to:
 Professor H-P Horny
 Institute of Pathology, University of Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany;
  • Accepted 16 December 2003


Aims: Although systemic mastocytosis (SM) with an associated clonal haematological non-mast cell lineage disease (SM-AHNMD) is a major subtype of SM, little is known about its frequency among myelogenous neoplasms, and mastocytosis in particular, or about AHNMD subtype frequencies.

Methods: Approximately 19 500 routine bone marrow biopsies were evaluated. Immunostaining with antibodies against tryptase, KIT, and CD25 and molecular analysis for detection of C-KIT point mutations were performed in approximately 550/4100 myelogenous malignancies including mastocytosis, almost all subtypes of myelodysplastic syndrome (MDS), myelodysplastic/myeloproliferative syndrome (MDS/MPD), MPD, and acute myeloid leukaemia (AML).

Results: SM was rare—it was diagnosed in only 64 bone marrows (0.3%) and made up 1.5% of myelogenous tumours. SM-AHNMD was the second most frequent subtype (20). SM-AHNMD was never included in the clinical differential diagnoses and was confirmed histologically in most cases only after appropriate immunostaining. The abnormal mast cell phenotype was confirmed by immunohistochemical demonstration of tryptase and CD25 coexpression. The following associated haematological neoplasms were found: MDS/MPS, AML, MPS, MDS, plasma cell myeloma, and unclassifiable myelogenous malignancy. C-KIT point mutations were detected in 16 of 20 cases.

Conclusions: SM-AHNMD can be diagnosed histologically in bone marrow trephines only after immunostaining with antibodies against tryptase, KIT, and CD25. Eighteen of 20 AHNMDs were of myeloid origin. C-KIT point mutations were present in 16 of 20 cases. The prognostic relevance of detecting SM associated with another haematological neoplasm remains unclear, but mast cell resistance to most cytoreductive agents is of major importance for treatment planning.