| Session: Mast cell disease |
| Case number: 167 |
Submitter(s): Irina Maric, Jennifer Stoddard, Weiming Fu, Pierre Noel.
Clinical history
Forty seven-year-old male presented with episodic diarrhea and hepatosplenomegaly. CBC data revealed: WBC 13.9, Hgb/HCT 13.8/43.3, PLT 605. WBC differential: 44% polys/bands, 34% lys, 8.8% monos, 13.1% eos. Absolute eosinophil count 1821, absolute monocyte count 1223. Serum tryptase was 334 ng/ml. No skin lesions. No signs of impairment of liver function or hypersplenism. Bone marrow biopsy was performed and diagnosed as systemic mastocytosis. Patient received only symptomatic therapy and no cytoreductive therapy. Yearly follow-up over next five-year period showed essentially the same clinical picture, CBC data, tryptase levels and bone marrow findings.
Details of gross/microscopic pathology:
Review of the peripheral blood smear showed mild RBC anisopoikilocytosis and target cells. WBC showed leukocytosis, eosinophilia, mild monocytosis. There was no significant left shift or dysplastic changes in myeloid elements. There was thrombocytosis with platelet clumps. No circulating mast cells or blasts.
Bone marrow biopsy (fixed in B-Plus and decalcified in RapidCal Immuno) revealed hypercellular marrow (70-80%) with multiple paratrabecular and perivascular mast cell aggregates, interstitial eosinophilia and few lymphoid collections associated with mast cell aggregates. Immunohistochemical staining for tryptase highlighted mast cells and showed that more than 25% of mast cells were spindle shaped. Mast cell aggregates involved 20-30% of marrow biopsy.
Bone marrow aspirate smear differential: 52% granulocytic precursors, 1% monocytes, 12% erythroid precursors, 21% lymphocytes, 10% eosinophils and 4% atypical mast cells. Mast cells were large, spindle-shaped or hypogranulated. There was no significant dysplasia in myeloid elements. Some of the megakaryocytes were atypical, with hypolobulated or monolobulated nuclei.
Immunophenotype (flow cytometry/immunohistochemistry):
Flow cytometric analysis of the bone marrow aspirate showed increase in mast cells (0.04%) positive for CD117, CD25, CD11c, CD35, CD59, CD63, CD69 and negative for CD2 and CD34. There were 0.3% blasts, 2.4% monocytes and 6.4% eosinophils in the bone marrow aspirate by flow cytometric analysis.
Cytogenetics:
Normal.
Molecular analysis:
RT-PCR/RFLP analysis for KIT D816V mutation was positive in bone marrow aspirate sample and peripheral blood sample. Nested RT-PCR for FIP1L1-PDGFRa fusion gene was negative.
Interesting feature(s) of submitted case:
The patient who presented with hypereosinophilia and monocytosis. Patient fulfilled WHO criteria for diagnosis of smoldering systemic mastocytosis. In addition to diagnosis of systemic mastocytosis with eosinophilia, should this patient carry diagnosis of chronic myelomonocytic leukemia (CMML) in view of pathological findings and clinical course.
Proposed diagnosis:
Systemic mastocytosis with eosinophilia.
Panel diagnosis:
agree with proposed diagnosis
Comments:
Studies performed by the panel: positive for D816V mutation, CD25+
PowerPoint:
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