title: Systemic mastocytosis with associated clonal haematological non-mast cell lineage diseases: a histopathological challenge.
abstract: OBJECTIVE
  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 19500 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.
authors.affiliation: Institute of Pathology, University of Lübeck, D-23538 Lübeck, Germany. horny@patho.mu-luebeck.de
authors.forename: H-P
authors.initials: HP
authors.lastname: Horny
authors.forename: K
authors.initials: K
authors.lastname: Sotlar
authors.forename: W R
authors.initials: WR
authors.lastname: Sperr
authors.forename: P
authors.initials: P
authors.lastname: Valent
mesh_terms: D000208:Acute Disease; D000368:Aged; D001706:Biopsy; D001853:Bone Marrow / Q000473:pathology; D005260:Female; D019337:Hematologic Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000473:pathology*; D006801:Humans; D007951:Leukemia, Myeloid / Q000473:pathology; D008297:Male; D008407:Mast Cells / Q000473:pathology; D034721:Mastocytosis, Systemic / Q000175:diagnosis / Q000235:genetics / Q000473:pathology*; D008875:Middle Aged; D009190:Myelodysplastic Syndromes / Q000473:pathology; D009363:Neoplasm Proteins / Q000235:genetics; D017354:Point Mutation; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics
chemical_list: D009363:Neoplasm Proteins; D019009:Proto-Oncogene Proteins c-kit