| Session: Mast cell disease |
| Case number: 037 |
Submitter(s): Tove V. Isaacson, Cem Akin, Megan S. Lim.
Clinical history
35-year-old woman presented at age 28 with pruritic, hyperpigmented maculopapular lesions. A punch biopsy revealed urticaria pigmentosa. Serum tryptase in 2005 was 118 ng/mL. A subsequent bone marrow examination showed active trilineage hematopoiesis without evidence of disease. A second bone marrow biopsy was obtained in October, 2006. A serum tryptase obtained at the time of biopsy was 153.0 ng/mL.
Details of gross/microscopic pathology:
Several large aggregates of spindle cells (>15 per aggregate), which featured oval, indented nuclei and variably granular cytoplasm, were noted in the bone marrow biopsy. These were seen in association with aggregates of lymphocytes and/or surrounding eosinophils. Bone marrow aspirate smears showed occasional single spindle cells in the background of normal trilineage hematopoietic maturation. Review of the peripheral blood smear was unremarkable.
Immunophenotype (flow cytometry/immunohistochemistry):
Immunophenotypic analysis of the mononuclear cells in the bone marrow aspirate by flow cytometry utilized a panel consisting of antibodies to CD2, CD25, CD45, and CD117. After gating on bright CD117-positive mast cells, it was determined that the mast cells co-expressed CD25 without CD2.
The spindle cell population in the bone marrow core biopsy showed strong, diffuse positivity for a tryptase immunohistochemical stain.
Cytogenetics:
N/A.
Molecular analysis:
The D816V c-kit mutation was detected in the bone marrow aspirate.
Interesting feature(s) of submitted case:
To enrich for mast cells, CD25-positive mononuclear cells were sorted and the D186V c-kit mutation was analysed by reverse transcriptase (RT)-PCR followed by restriction fragment length polymorphism (RFLP) analysis.
Analyses for the mutation in unfractionated bone marrow mononuclear cells or peripheral blood were negative. Without fractionation, the patient would have been considered negative for theD816V c-kit mutation and possibly would have received imatinib (Gleevec), which is not therapeutically beneficial for patients carrying the D816V c-kit mutation.
Proposed diagnosis:
Systemic mastocytosis.
Panel diagnosis:
agree with proposed diagnosis
Comments:
Panel comment: indolent systemic mastocytosis. Studies performed by the panel: no amplification for c-kit, CD25+
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