title: A case of mast cell leukaemia with exon 9 KIT mutation and good response to imatinib.
abstract: BACKGROUND
  Mastocytosis is a myeloproliferative neoplasm characterized by the excessive proliferation of mast cells. Mast cell leukaemia (MCL), the aggressive form of this disease, requires cytoreductive therapy, such as cladribine, interferon-alpha-2b and, most recently, tyrosine kinase inhibitors - dasatinib or imatinib.
  
  
  METHODS
  We present a case of a 56-yr-old female patient with aleukaemic MCL in whom the typical KIT-D816V mutation was not detected. Sequencing of the entire coding sequence of KIT gene revealed a somatic mutation in exon 9 (p.A502_Y503dup). This mutation was previously reported in patients with gastrointestinal stromal tumours (GIST). Considering the good response to imatinib in such patients, therapy with imatinib was attempted in our patient. The treatment tolerance and outcomes were very good, with reduced mast cell infiltration of the bone marrow, normalization of the serum tryptase concentration and resolution of the clinical signs and symptoms.
  
  
  CONCLUSIONS
  In the absence of the KIT-D816V in systemic forms of mast cell proliferation, a search for other mutations is indicated, preferably by sequencing the entire KIT gene, as this can influence the choice of treatment. The finding of the p.A502_Y503dup in exon 9, a mutation which has been observed in GIST but not previously reported in any form of aggressive mastocytosis, can be associated with a good response to imatinib in both diseases.
authors.affiliation: Department of Hematology and Transplantology, Medical University of Gdansk, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Mital
authors.forename: Anna
authors.initials: A
authors.lastname: Piskorz
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Lewandowski
authors.forename: Bartosz
authors.initials: B
authors.lastname: Wasąg
authors.forename: Janusz
authors.initials: J
authors.lastname: Limon
authors.forename: Andrzej
authors.initials: A
authors.lastname: Hellmann
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001483:Base Sequence; D001549:Benzamides; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D005091:Exons; D005260:Female; D006801:Humans; D000068877:Imatinib Mesylate; D007946:Leukemia, Mast-Cell / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D008875:Middle Aged; D009154:Mutation; D010879:Piperazines / Q000627:therapeutic use*; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics*; D011519:Proto-Oncogenes; D011743:Pyrimidines / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D004273:DNA, Neoplasm; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit