| Session: Mast cell disease |
| Case number: 112 |
Submitter(s): Curtis A. Hanson, Chin Y. Li.
Clinical history
The patient was a 19-year-old college student. His symptoms began at the age of 15 with recurring episodes of tachycardia, flushing, headache, and sharp abdominal pain that became more acute over time. Extensive workups for these episodes were negative for any known etiology, including carcinoid, pheochromocytoma, and complement disorders. At the time of this evaluation, serum tryptase was found to be elevated at 157.5 and urine histamine levels were slightly elevated. Physical examination was normal.
CBC: Hgb 15.1 g/dL; WBC 8.6 x 109/L; PLT 237 x 109/L.
WBC Differential (%): Neutrophils 63.0; lymphocytes 27.0; monocytes 10.0.
Details of gross/microscopic pathology:
The peripheral blood smear was normal in appearance. No eosiniophilia was seen. The bone marrow aspirate and biopsy (B5-fixed; acid decal) were slightly hypocellular for age (50%). There was normal trilineage hematopoiesis present. The bone marrow aspirate showed atypical spindle-shaped mast cells as well as partially granulated mast cells. The bone marrow biopsy showed no large lesions of mast cells with only focal collections of atypical spindle-shaped mast cells present most predominantly in a perivascular pattern.
Immunophenotype (flow cytometry/immunohistochemistry):
Immunohistochemical stains were performed on paraffin-embedded sections of bone marrow biopsy using antibodies against the following antigens: CD2, CD25, CD117, tryptase, and phospho-STAT5. The immunostains showed increased atypical mast cells that stained with tryptase, phospho-STAT5, CD117, and CD25; the mast cells appeared to be negative with CD2.
Flow cytometric immunophenotyping was performed on the bone marrow specimen with antibodies directed against CD2, CD25, CD69, and CD117. The CD117 (bright) and CD69 positive mast cells showed aberrant coexpression of CD25 and no expression of CD2.
Cytogenetics:
Cytogenetic studies of the bone marrow showed a normal karyotype, 46,XY, in 20 of 20 metaphases.
Cytogenetic (FISH) studies performed on the bone marrow specimen showed that 0% of 200 nuclei had 1 CHIC2 and 2 FGFR3 signals. 0% of nuclei had 3 FIP1L1/PDGFRA fusion signals. These studies were normal.
Molecular analysis:
An allele-specific oligonucleotide polymerase chain reaction (ASO-PCR) analysis for the KIT-Asp816Val mutation was performed. This Asp816Val mutation was absent.
Interesting feature(s) of submitted case:
This case shows the morphological difficulty in recognizing minimal bone marrow involvement by mast cell disease and the clinical difficulty in recognizing this disorder in nontraditional clinical presentations. Careful morphologic review of the bone marrow together with immunohistochemical stains in the bone marrow biopsy and flow cytometric immunophenotyping for aberrant mast cell phenotypes are critical in making this diagnosis. Phospho-STAT5 staining and flow cytometric immunophenotyping may help distinguish reactive mast cells from true mast cell disease.
Proposed diagnosis:
Minimal bone marrow involvement by indolent systemic mastocytosis.
Panel diagnosis:
agree with proposed diagnosis
Comments:
Panel comment: unusual age group. Studies performed by the panel: WT c-kit, CD25- (?)
Images:
 |
Figure 1 |
 |
Figure 2 |
 |
Figure 3 |
 |
Figure 4 |
 |
Figure 5 |
 |
Figure 6 |
 |
Figure 7 |
 |
Figure 8 |
 |
Figure 9 |
Back to Top
Back to Cases by Session
Back to Cases by Contact Submitter