| Session: Mast cell disease |
| Case number: 140 |
Submitter(s): Hongyu Ni, Bashar Dabbas.
Clinical history
This is a 47 year-old male with history of thrombocytosis for 8 years. He had one episode of arterial thrombosis of left common iliac artery in 2002. In 1998 his hemoglobin was 16.2 and his platelet count was 419,000; hemoglobin was 17.8 and platelet count was 659,000 in 2002. Physical examination demonstrated no hepatosplenomegaly. There was no lymphadenopathy. No skin lesions were identified at the time of presentation. The patient was on plavix, Prevacid, and Lesco.
Laboratory studies are as follows: WBC 15.1 k/ul, RBC 5.70 M/ul, HgB 16.3 g/dl, HCT 49.5%, MCV 86.8 fl., MCH 28.6 pg, RDW 14.1%, Platelets 922 k/ul. The differential count shows neutrophils 80%, lymphocytes 13%, monocytes 5%, eosinophils 2%. Serum total tryptase level is pending.
Details of gross/microscopic pathology:
Peripheral blood shows mild neutrophilia. Neutrophil granulation and segmentation appear normal. No significant left shift is present. Blasts are not increased. Eosinophils and basophils are not increased. Platelets appear markedly increased in number and are largely normal in appearance.
Bone marrow core biopsy (2 x 0.3 cm) was obtained form iliac crest and fixed in B-Plus Fixative. Bone marrow aspirate smears were stained with a Wright-Giemsa staining method. The bone marrow H&E sections and aspirate smears demonstrate mildly hypercellular marrow for age (60%) with trilineage hematopoiesis (M:E ratio of 2.5:1) and megakaryocytic hyperplasia. Megakaryocytes show pleomorphism with large hyperlobated nuclei. There is no significant granulocytic left shift. Myeloid blasts are not increased. Erythroid precursors are normal in number and exhibit orderly maturation. Reticulin stain shows no definitive evidence of reticulin fibrosis. Multifocal perivascular and peritrabecular cellular aggregates are present, which consist of small lymphocytes surrounded by mast cells. The mast cells are spindle- or polygonal-shaped with moderate amount of pale cytoplasm. Bone marrow aspirate smears show occasional mast cells. There is no significant dyspoiesis.
Immunophenotype (flow cytometry/immunohistochemistry):
Immunohistochemical stains show that each aggregate consists of more than 15 mast cells, which are positive for CD117 and tryptase.
Immunophenotypic analysis of bone marrow aspirate by flow cytometry did not detect increased mast cells (based on CD117 staining).
Cytogenetics:
Cytogenetic analysis reveals a normal male karyotype. FISH analysis with probe specific for BCR-ABL shows a normal signal pattern. There is no evidence of BCR-ABL fusion gene product.
Molecular analysis:
Molecular studies by PCR are positive for JAK2 mutation with 13% mutant allele detected.
Interesting feature(s) of submitted case:
This case demonstrates a Philadelphia chromosome negative chronic myeloproliferative disorder patient with co-existing mastocytosis. The morphologic features are most consistent with essential thrombocythemia.
Proposed diagnosis:
1). Chronic myeloproliferative disorder, most likely essential thrombocythemia
2). Mastocytosis.
Panel diagnosis:
SM-AHNMD/chronic myeloproliferative disease
Comments:
Studies performed by the panel: no amplification for c-kit, WT JAK-2
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