title: Chronic mast cell leukemia (MCL) with KIT S476I: a rare entity defined by leukemic expansion of mature mast cells and absence of organ damage.
abstract: Mast cell leukemia (MCL) is a rare, life-threatening malignancy defined by a substantial increase in neoplastic mast cells (MCs) in bone marrow (BM) smears, drug-resistance, and a poor prognosis. In most patients, the survival time is less than 1 year. However, exceptional cases may present with a less malignant course. We report on a 49-year-old female patient with MCL diagnosed in 2013. In February 2013, first symptoms, including flushing, headache, and diarrhea, were recorded. In addition, mild anemia was detected. The disease was characterized by a massive increase in well-granulated, mature, and often spindle-shaped MCs (80 %) in BM smears. The serum tryptase level amounted to 332 ng/mL. Like in most other MCL patients, no skin lesions were detected. However, unlike in other patients, tryptase levels remained stable, and no other signs or symptoms of MCL-induced organ damage were found. Sequencing studies revealed an isolated S476I point mutation in KIT but no mutation in codon 816. The patient received histamine receptor blockers but refused cytoreductive therapy. After 9 months, still no progression or organ damage was detected. However, progression with transformation to acute MCL occurred after 12 months. We propose that the chronic type of MCL with stable conditions, absence of organ damage, and a mature MC morphology is recognized as a distinct entity that should be distinguished from the acute variant of MCL.
authors.affiliation: Department of Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria, peter.valent@meduniwien.ac.at.
authors.forename: Peter
authors.initials: P
authors.lastname: Valent
authors.forename: Jörg
authors.initials: J
authors.lastname: Berger
authors.forename: Sabine
authors.initials: S
authors.lastname: Cerny-Reiterer
authors.forename: Barbara
authors.initials: B
authors.lastname: Peter
authors.forename: Gregor
authors.initials: G
authors.lastname: Eisenwort
authors.forename: Gregor
authors.initials: G
authors.lastname: Hoermann
authors.forename: Leonhard
authors.initials: L
authors.lastname: Müllauer
authors.forename: Christine
authors.initials: C
authors.lastname: Mannhalter
authors.forename: Michael
authors.initials: M
authors.lastname: Steurer
authors.forename: Peter
authors.initials: P
authors.lastname: Bettelheim
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Horny
authors.forename: Michel
authors.initials: M
authors.lastname: Arock
mesh_terms: D001856:Bone Marrow Examination; D049109:Cell Proliferation / Q000187:drug effects; D002908:Chronic Disease; D005260:Female; D006801:Humans; D007946:Leukemia, Mast-Cell / Q000235:genetics* / Q000473:pathology; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008875:Middle Aged; D020125:Mutation, Missense; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics*
chemical_list: D047428:Protein Kinase Inhibitors; D019009:Proto-Oncogene Proteins c-kit