Pediatric Gastric GIST With SDHA Truncation Despite Retained SDHB Staining: A Case Report.

BACKGROUND

Loss of SDHB by immunohistochemistry (IHC) is a practical screening marker for SDH-deficient GIST.

OBSERVATION: A 14-year-old boy had a gastric GIST (KIT/DOG1 positive). Next-generation sequencing identified a truncating SDHA variant (c.1401T>A, p.Cys467Ter). Notably, SDHB IHC was strongly positive despite molecular evidence of SDH deficiency.

CONCLUSIONS

Retained SDHB staining does not exclude SDH-deficient GIST. When clinicopathologic features suggest SDH deficiency, comprehensive molecular testing-including germline assessment-should be pursued, even in the context of SDHB positivity, to avoid false reassurance and to inform counseling and surveillance.