| Session: Mast cell disease |
| Case number: 228 |
Submitter(s): Vishnu V. B. Reddy.
Clinical history
This is a 65 year old female with three month history of abdominal bloating and weakness. Routine CBC showed mild leukocytosis (14 k/uL) with monocytosis (1500 absolute monocyte count), mild anemia (HB 11.5 gm/dL) and thrombocytopenia (90 k/uL). Later a bone marrow aspiration and biopsy was performed which showed hypercellular marrow (> 75% cellularity) with several early myeloid / monocytic elements and few clusters of cells with granular cytoplasm.
Details of gross/microscopic pathology:
Peripheral blood: Mild leukocytosis with mild myeloid left-shift (rare blasts, few promyelocytes and myelocytes). Many of the neutrophils were hypo-segmented and some are hypogranular. Several monocytes are noted.
Bone marrow aspirate / biopsy: Hypercellular marrow (>75% cellular) with myeloid predominance and left-shift. Erythroid and megakaryocytes are reduced. Few small clusters of mast cells with intense cytoplasmic granules found. Bony trabeculae are unremarkable.
Fig 1- Peripheral blood (monocytosis). Fig 2 - 4 - Bone marrow aspirate showing abnormal myeloid cells and mast cells. Fig 5 - Mast cell aggregates in bone marrow biopsy (CD117+).
Immunophenotype (flow cytometry/immunohistochemistry):
Flow cytometry Few early myeloid precursors (CD117+, CD34+ and CD33) and several monocytes (CD14+, CD64+ and CD33+) are found. The few remaining are mature linage T-cells expressing CD2, CD4 normal CD4/CD8 subsets. Rare B-cells are polyclonal.
Cytochemical Stains Several myeloperoxidase (MPO) and non-specific esterase (NSE) cells were seen on bone marrow biopsy aspirate smears. Giemsa and toluidine blue stain highlighted mast cells in the biopsy.
Immunohistochemical stains [ndash] CD117+ and tryptase+ mast cell clusters were found in the marrow biopsy. Additionally, mast cells are positive for CD23 and negative for CD2 and CD25.
Cytogenetics:
Cytogenetic Analysis Bone marrow aspirate was positive for trisomy 8 and no other clonal abnormalities detected.
Molecular analysis:
c-kit mutation (c-kit D816V was negative) and FISH for bcr/abl was negative.
Interesting feature(s) of submitted case:
Peripheral blood and bone marrow morphology was compatible with myelodysplastic syndrome / chronic myelomonocytic leukemia (MDS/CMML).
Bone marrow biopsy and aspirate smears contained clusters of mast cells (CD117+, CD23+ and tryptase+). Also, significant myeloid hypeplasia was noted. Clustering of mast cells was more compatible with systemic mast cell disease.
Proposed diagnosis:
Chronic myelomonocytic leukemia (CMML/MDS) with associated systemic mast cell disease
Systemic mast cell disease with associated clonal hematologic non-mast cell disease (SM-AHNMD).
Panel diagnosis:
Differential diagnosis includes systemic mastocytosis/mast cell leukemia and SM-AHNMD
Comments:
Studies performed by the panel: WT c-kit, CD25-
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