| Session: Mast cell disease |
| Case number: 103 |
Submitter(s): Young S. Kim, Vinod Pullarkat.
Clinical history
83 year old male with 5-year history of indolent systemic mastocytosis. WBC-5.2K/ul, RBC- 3.13 M/ul, Hgb-10.0 G/dl, HCT-29.0%, plt-248, Seg-66/0%, Lymph-19.3%, Tryptase was elevated (115, normal 0-10). Medication- Doxazosin, Zyrtec, and Cimetidine. After 2 years follow up, the patient developed lymphadenopathy with large pelvic node. Biopsy of node showed low grade B-cell lymphoma.
Details of gross/microscopic pathology:
Bone marrow was hypercellular with clusters of mast cells, often spindled, comprising 15% of cellularity. Abundant lymphoid aggregates, composed of small lymphocytes, were present.
Immunophenotype (flow cytometry/immunohistochemistry):
Flow cytometry showed lambda monoclonal B-cells, positive for CD19 and CD22 and negative for CD5, CD23, CD10, CD11c, CD103, CD25, and FMC7.
Paraffin immunohistochemistry showed atypical mast cell clusters, positive for tryptase, CD117 and CD25. The associated lymphoid aggregates were predominantly CD20 positive B-cells, co-expressing BCL-2 and CD43, but are negative for CD5, CD23, CD10, and BCL-1.
Cytogenetics:
46, XY
Molecular analysis:
Mast cells and lymphoid aggregates are microdissected using PALM laser microdissection system. Genomeic DNA was extracted from mast cells and lymphocytes seperately. Exon 17 of KIT gene was amplified by semi-nested PCR on both samples. Immunoglobulin heavy chain gene rearrangement analysis was performed using standard methods.
The KIT mutation D818V was detected in the clusters of mast cells, consistent with systemic mastocytosis. The KIT mutation is not identified in B-cells. The B-cells were monoclonal by immunoglobulin heavy chain gene rearrangement analysis.
Interesting feature(s) of submitted case:
Systemic mastocytosis can be associated with lymphoproliferative disorders. the relationship between neoplastic mast cells and lymphocytes remains unclear.We describe a patient with indolent systemic mastocytosis whose marrow showed B-cell lymphoma. By detecting the KIT mutation D816V in the microdissected mast cells, but not in the neoplastic B-lymphocytes, we demonstrate the distinct clonal origins of mastocytosis and lymphoma when these two entities coexist. According to WHO classification, patients with myeloid or lymphoid malignancies coexisting with SM could be included under SM-AHNMD. However, the clinical and pathologic features of these entities are different. Unlike SM with myeloid malignancies where mastocytosis and myeloid neoplasm are often diagnosed concurrently, reported patients with SM-LPD have a long history of indolent SM. This temporal profile suggests a different pathogenesis for these two entities.
Proposed diagnosis:
Indolent systemic mastocytosis coexisting with low grade B-cell lymphoma.
Panel diagnosis:
agree with proposed diagnosis
Comments:
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