| Session: Mast cell disease |
| Case number: 171 |
Submitter(s): Eric D. Hsi.
Clinical history
A 50 year old woman presented with pleural effusion and rash. She had a history of relapsed Hodgkin lymphoma treated with autologous bone marrow transplantation 11 years prior and melanoma 5 years prior. Work-up revealed a lytic lesion of her right femur. A biopsy of the femur was performed.
Details of gross/microscopic pathology:
Currettings showed a dense proliferation of bland spindled cells with admixed eosinophils and lymphoid aggregates. Areas with unremarkable hematopoietic bone marrow were also seen.
Immunophenotype (flow cytometry/immunohistochemistry):
Tryptase Positive in spindled cells
CD25 Positive in spindled cells
CD2 Negative in spindled cells
Phospho-STAT5 (Y694/Y699) Postive in spindled cells (nuclear pattern).
Cytogenetics:
None.
Molecular analysis:
None.
Interesting feature(s) of submitted case:
This patient has a complicated history. She underwent a random bone marrow biopsy shortly after this diagnosis of SMCD, which showed focal mast cell lesions but no evidence of active hematologic malignancy or melanoma. She was treated with antihistamines with resolution of her rash. She has been followed with no evidence of malignancy and was last seen in September 2006 with no evidence of disease (7.5 years after the diagnosis of mast cell disease). Despite the prior history of a hematopoietic non-mast cell lineage disease (Hodgkin lymphoma), the long interval between these diagnoses and clinical course suggests indolent systemic mastocytosis.
The phospho-STAT5 pattern is abnormal and characteristic of systemic mast cell disease. We have investigated a series of SMCD of various types and have found this to be a reliable and specific marker of SMCD. Normal and hyperplastic mast cells lack detectable nuclear phospho-STAT5. This likely reflects the underlying abnormal tyrosine kinase activity resulting from activating mutations in KIT (KIT D816V most commonly). We propose mast cell nuclear phospho-STAT5 as an additional minor criterion for the diagnosis of SMCD.
Proposed diagnosis:
Systemic mast cell disease (indolent) demonstrating abnormal phospho-STAT5 immunostaining pattern in a patient with prior history of Hodgkin lymphoma, in remission.
Panel diagnosis:
agree with proposed diagnosis
Comments:
Panel comment: probably aggressive SM. Studies performed by the panel: positive for D816V mutation, CD25+
PowerPoint:
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