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Answer
The histology shows spindle cells in a fascicular/storiform pattern - classic for a Gastrointestinal Stromal Tumor (GIST).
The specific marker for GIST is CD 117 (c-KIT).
Answer: A) CD 117
Why CD 117?
- GIST is the most common mesenchymal tumor of the GI tract, arising from the interstitial cells of Cajal
- These cells express c-KIT (CD117), a tyrosine kinase receptor - positive in ~95% of GISTs
- The histology here shows intersecting bundles of spindle cells on H&E - the classic GIST appearance
- Location on the greater curvature of the stomach is the most common site for GIST (~60% of GISTs occur in the stomach)
Why not the others?
| Marker | Associated Tumor |
|---|---|
| CD 117 | GIST ✓ |
| CD 19 | B-cell lymphoma |
| CD 23 | Follicular dendritic cell tumor / CLL |
| S-100 | Neural tumors, melanoma, schwannoma |
Additional point: DOG-1 (Discovered On GIST-1) is another highly specific marker for GIST. Treatment of metastatic/unresectable GIST uses imatinib (a c-KIT inhibitor).
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