| Session: Mast cell disease |
| Case number: 236 |
Submitter(s): Brian Olsen
Clinical history
62 year old female presenting in 2004 with DVT, following which mild leukocytosis and marked thrombocytosis were discovered. She was otherwise asymptomatic, with no report of mediator release symptoms.
Details of gross/microscopic pathology:
2004: Marked thrombocytosis, with platelet atypia. Mild neutrophilia. Negative for leukoerythroblastosis, tear-drop poikylocytosis, basophilia or monocytosis. Markedly hypercellular bone marrow, with panhyperplasia, megarkaryocytic dysplasia, 1-2+ reticulin fibrosis, and no excess of blast cells. 2006: Pancytopenia, with RBC macrocytosis. Moderately hypocellular bone marrow, with evidence of trilineage dyshematopoiesis, and an excess of blasts (10-15%). 2007: Pancytopenia, with circulating blast forms (8-9%). Markedly hypercellular bone marrow, with evidence of transformation to acute leukemia (30-40%) marrow blasts), clusters of plasmacytoid monocytes, background of trilineage dyshematopoiesis, 2+ reticulin fibrosis. An excess of atypical mast cells also identified, by immunohistochemistry (see below), having rounded morphology, and found singly and in small clusters.
Immunophenotype (flow cytometry/immunohistochemistry):
Blast cells: dinm cytoplasmic MPO+, dim CD13+, dim CD33, CD117+, dim CD34, TDT+, HLA-DR+ (by flow). MPO+, TDT+, CD117 (by ipox). Mast cells: Mast cell tryptase+, CD117+, CD2-, CD25- (by opox). Plasmacytoid monocytes: CD4+, CD68+, CD45RA+, CD123+, CD56- (by ipox).
Cytogenetics:
2004: Normal femal karyotype. Negative for bcr/abl rearrangement by FISH. 2006 and 2007: Trisomy 21
Molecular analysis:
Positive for Jak2 V617F mutation by allele-specific PCR (2004). C-kit mutation analysis pending.
Interesting feature(s) of submitted case:
Rare example of myelomastocytic leukemia, part of the spectrum of myelomastocytic overlap syndromes. This particular sub-type is defined by the presence of large numbers of immature, mast cell-lineage cells, found in association with an advanced myeloid neoplasm, and not meeting criteria for diagnosis of mastocytosis. This case has evolved from a previously diagnosed, bcr/abl negative, Jak2 V617F mutation positive CMPD. This case was seen in consultation by Dr. Attilio Orazi, of the University of Indiana. Reference: Valent, et al, Leukemia Research 25 (2001) 595-602
Proposed diagnosis:
Myelomastocytic leukemia, evolving from bcr/abl negative, Jak2 V617F positive CMPD (pre-fibrotic CIMF).
Panel diagnosis:
Ph- chronic myeloproliferative disease
Comments:
Panel comment: systemic mastocytosis excluded. Studies performed by the panel: WT c-kit, CD25-, V617F+. Additional information: CBC 2004 WBC 12.9k/cumm with ANC 10.1k/cumm, hemoglobin 13.6g/dL, platelet count 986k/cumm, CBC 2006 WBC 2.7k/cumm, hemoglobin 11.1g/dL, platelet count 124k/cumm, CBC 2007 WBC 6.8k/cumm, hemoglobin 10.4g/dL, platelet count 61k/cumm
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