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Immunohistochemistry and molecular analyses in myeloid sarcoma of the breast in a patient with relapse of NPM1-mutated and FLT3-mutated AML after allogeneic stem cell transplantation
  1. Matthias Choschzick1,
  2. Ulrike Bacher2,
  3. Francis Ayuk2,
  4. Annette Lebeau1
  1. 1Department of Pathology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
  2. 2Interdisciplinary Clinic for Stem Cell Transplantation, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
  1. Correspondence to Dr Matthias Choschzick, Department of Pathology, University Medical Centre Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany; mchoschz{at}


Myeloid sarcoma of the breast is a rare manifestation of acute myeloid leukaemia (AML). This report describes a patient who was diagnosed with AML FAB M2. Molecular analysis showed evidence of an NPM1 mutation (subtype A) and internal tandem duplications of the FLT3 gene (FLT3-ITD). Eight months after allogeneic stem cell transplantation, the patient developed a palpable mass in the left breast initially suspected as breast carcinoma. Core needle biopsy of the lesion resulted in diagnosis of myeloid sarcoma. Molecular analysis of formalin-fixed specimens of the breast tumour confirmed the known FLT3 and NPM1 gene mutations. Immunohistochemically, an aberrant cytoplasmic staining pattern for NPM1 and overexpression of FLT3 were demonstrated. The myeloid sarcoma showed complete transient resolution following treatment with the kinase inhibitor sorafenib. However, the patient developed bone marrow relapse and died in fatal cerebral haemorrhage 1 year after initial diagnosis of AML. In summary, combined molecular and immunohistochemical examination of NPM1 and FLT3 is helpful in the diagnosis of extramedullary manifestations of AML in core needle biopsies.

  • Acute myeloid leukaemia (AML)
  • FLT3-ITD
  • immunohistochemistry
  • myeloid sarcoma
  • myeloproliferative disease
  • NPM1 mutation
  • PCR

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  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.