| Session: Mast cell disease |
| Case number: 019 |
Submitter(s): Kaaren K. Reichard.
Clinical history
The patient is a 66-year-old woman who has been previously healthy. She has no significant medical or surgical history. Medication list is unknown. She presents to her physician complaining of fatigue and is found to have pancytopenia on a CBC. WBC 2.4, RBC 2.8, Hgb 9.0, plt 56K, MCV 101, RDW 16.1%.
Details of gross/microscopic pathology:
Peripheral blood: Differential count: 62% neut, 27% lymph, 10% mono, 1% eos. Rare myeloid-appearing blasts. No overt circulating mast cells.
Bone marrow aspirate (figures 1,2 and 3): Spicular and hypercellular. Erythroid predominance with shift to immaturity and dysplastic features characterized by circumferential cytoplasmic vacuolization, nuclear contour irregularities and multilobation and mild nuclear:cytoplasmic dyssynchrony. Granulocytic precursors are relatively decreased in number with mild atypia (megaloblastoid forms and abnormal localization of cytoplasmic granules). Increased myeloid blasts, some smaller in size, with scant cytoplasm and minimal granulation. Numerous mast cells, many with spindled morphology, within the particles and in the smear. Megakaryocytes are decreased with rare small forms seen. 500 cell differential: erythroid 69%, myeloid blasts 18%, other 13%.
Bone marrow core biopsy: Hypercellular with abnormal, thickened bone and paratrabecular collections of mononuclear, mast-cell-appearing cells (figure 4 and 5). Large groups and clusters of blastic mononuclear cells in the interstitium (figure 5). Left-shifted erythroid lineage not in well-formed colonies.
Immunophenotype (flow cytometry/immunohistochemistry):
Tryptase highlights mast cells, many with spindled morphology, both in a paratrabecular distribution as well as interstitially increased (figure 6). CD34 shows increase blasts (~10-15%) (figure 7). Myeloperoxidase shows an increase in immature cells well away from the typical paratrabecular location (figure 8). Hemoglobin A show clusters of immature normoblasts (figure 9).
Flow cytometry: (Figure 10. Red, blasts; Green, lymphocytes; Blue, maturing granulocytes; Yellow, erythoid). There is an increased population (~8-10%) of myeloid blasts (CD34+, CD117+, CD13+, CD33+, HLA-DR+) in a background of ~50-55% erythroid lineage cells CD45(-), glycophorin+.
Cytogenetics:
Conventional cytogenetics revealed a normal female karyotype.
Molecular analysis:
Interesting feature(s) of submitted case:
Unsuspected systemic mastocytosis with an associated high grade myeloid malignancy, best classified as acute erythroid leukemia (erythroleukemia, erythroid/myeloid, M6a). M6a is reportedly rare as the associated haematological non-mast cell lineage disorder.
Proposed diagnosis:
Systemic mastocytosis with associated high grade clonal haematological non-mast cell lineage disorder (best classified as acute erythroid leukemia).
Panel diagnosis:
agree with proposed diagnosis
Comments:
Studies performed by the panel: positive for D816V mutation, CD25+
PowerPoint:
Presentation Link
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