| Session: Mast cell disease |
| Case number: 096 |
Submitter(s): Ezra D. Ellis, Michael W. Beaty.
Clinical history
58 year old male with no previous exposures or therapies presented with acute left back pain and splenomegaly. Chest x-ray demonstrated a left lower lobe infiltrate. A bone marrow biopsy performed on the outside was worrisome for "acute myelogenous leukemia of unknown type". The patient's induction regimen was beta-cytosine arabinoside, daunorubicin, and etoposide. He had several relapses and was later treated with cyclophosphamide and etoposide.
CBC
WBC 58.2 x 109/L
Hgb 11.7 g/dL
Platelets 96.0 x 109/L
Peripheral blood differential: 7% segmented neutrophils; 9% lymphs; 84% monocytes with immature and atypical forms
Details of gross/microscopic pathology:
Gross: Aspirate smears and bone marrow biopsy treated with rapid decal and B5 fixation
A. Original Diagnostic Marrow Bone marrow differential
Blasts 17%
Monocytes 65%
Promyelocytes 4%, Neutrophil myelocytes 1%, Neutrophil band 1%, Neutrophil segs 2%, Eosinophils 1%, Mid Erythrocytes 1%, Lymphocytes 8%
Bone marrow aspirate smears demonstrated atypical and immature cells with convoluted, vacuolated nuclei with abundant cytoplasm consistent with monocyte precursors. No auer rods are identified.
B. Post-Induction Marrow: Panhypoplasia with sheets of mast cells easily identified. No residual leukemia identified.
Immunophenotype (flow cytometry/immunohistochemistry):
CD 45 verses side scatter revealed atypical cells of the monocyte gate represented 84% of the total.
Positive for: CD13, CD33, CD15, CD14, CD38 and HLA-DR;
Negative for: CD3, CD7, CD56, CD34, CD19 and CD20
The blast gate (3%) demonstrated CD34, CD38/ HLA-DR positive cells
Immunohistochemistry
Clusters positive for: Mast Cell Tryptase, CD 117a (C-Kit); CD2 negative
Back ground leukemic cells were positive for: Muramidase, and CD68
Histochemistry:
Monocytic cells Butyrate esterase positive; PAS and myeloperoxidase negative.
Cytogenetics:
Normal Karyotype 46 (X,Y).
Molecular analysis:
Not performed.
Interesting feature(s) of submitted case:
Summary: Acute Monocytic Leukemia (FAB sub type M5a) with a separate spindle cell population (Clusters greater than 15 cells) that is positive for C-Kit (CD117a), and Mast Cell Tryptase. The mast cell clusters were not recognized on the initial biopsy, but were easily identified in subsequent post-induction therapy marrow specimens. The spindled, reniform nature of acute monocytic leukemia may have added to the difficulty of recognizing the mast cell population.
Proposed diagnosis:
Systemic Mastocytosis associated with Acute Monocytic Leukemia (FAB subtype M5a).
Panel diagnosis:
SM-AHNMD/acute monocytic leukemia
Comments:
Studies performed by the panel: psitive for D816V mutation, CD25+
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