Succinate Dehydrogenase-Deficient GISTs: A Clinicopathologic, Immunohistochemical, and Molecular Genetic Study of 66 Gastric GISTs With Predilection to Young Age

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Abstract

Most gastrointestinal stromal tumors (GISTs) are driven by KIT or PDGFRA-activating mutations, but a small subset is associated with loss of function of the succinate dehydrogenase (SDH) complex of mitochondrial inner membrane proteins. This occurs by germline mutations of the SDH subunit genes and hitherto unknown mechanisms. SDH-deficient GISTs especially include pediatric GISTs and those associated with Carney triad (CT) or Carney-Stratakis syndromes (CSSs); the latter 2 also include paraganglioma as a component. SDH-deficient GISTs were identified in this study on the basis of immunohistochemical loss of succinate dehydrogenase subunit B (SDHB), which signals functional loss of the SDH complex. We found 66 SDH-deficient GISTs among 756 gastric GISTs, with an estimated frequency of 7.5% of unselected cases. Nearly, all gastric GISTs in patients <20 years, and a substantial percentage of those in patients <40 years, but only rare GISTs in older adults were SDH deficient. There was a female predominance of over 2:1. Two patients each had either pulmonary chondroma or paraganglioma (CT), but none of the examined cases had SDH germline mutations (CSS) or somatic KIT/PDGFRA or BRAF mutations. SDH-deficient GISTs were often multiple and typically showed plexiform muscularis propria involvement and epithelioid hypercellular morphology. They were consistently KIT-positive and DOG1/Ano 1-positive and almost always smooth muscle actin negative. Tumor size and mitotic activity varied, and the tumors were somewhat unpredictable with low mitotic rates developing metastases. Gastric recurrences occurred in 11 patients, and peritoneal and liver metastases occurred in 8 and 10 patients, respectively. Lymph node metastases were detected in 5 patients, but lymphovascular invasion was present in >50% of cases studied; these 2 were not related to adverse outcome. Seven patients died of disease, but many had long survivals, even with peritoneal or liver metastases. All 378 nongastric GISTs and 34 gastric non-GIST mesenchymal tumors were SDHB positive. SDH-deficient GISTs constitute a small subgroup of gastric GISTs; they usually occur in children and young adults, often have a chronic course similar to that of pediatric and CT GISTs, and have potential association with paraganglioma, necessitating long-term follow-up.

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PDGFRA activating mutations in gastrointestinal stromal tumors.

Michael Heinrich, Christopher L Corless, Anette Duensing … (2003)

Most gastrointestinal stromal tumors (GISTs) have activating mutations in the KIT receptor tyrosine kinase, and most patients with GISTs respond well to Gleevec, which inhibits KIT kinase activity. Here we show that approximately 35% (14 of 40) of GISTs lacking KIT mutations have intragenic activation mutations in the related receptor tyrosine kinase, platelet-derived growth factor receptor alpha (PDGFRA). Tumors expressing KIT or PDGFRA oncoproteins were indistinguishable with respect to activation of downstream signaling intermediates and cytogenetic changes associated with tumor progression. Thus, KIT and PDGFRA mutations appear to be alternative and mutually exclusive oncogenic mechanisms in GISTs.

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Gain-of-Function Mutations of c-kit in Human Gastrointestinal Stromal Tumors

S Hirota (1998)

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Defects in succinate dehydrogenase in gastrointestinal stromal tumors lacking KIT and PDGFRA mutations.

Katherine A Janeway, Su Kim, Maya Lodish … (2011)

Carney-Stratakis syndrome, an inherited condition predisposing affected individuals to gastrointestinal stromal tumor (GIST) and paraganglioma, is caused by germline mutations in succinate dehydrogenase (SDH) subunits B, C, or D, leading to dysfunction of complex II of the electron transport chain. We evaluated the role of defective cellular respiration in sporadic GIST lacking mutations in KIT or PDGFRA (WT). Thirty-four patients with WT GIST without a personal or family history of paraganglioma were tested for SDH germline mutations. WT GISTs lacking demonstrable SDH genetic inactivation were evaluated for SDHB expression by immunohistochemistry and Western blotting and for complex II activity. For comparison, SDHB expression was also determined in KIT mutant and neurofibromatosis-1-associated GIST, and complex II activity was also measured in SDH-deficient paraganglioma and KIT mutant GIST; 4 of 34 patients (12%) with WT GIST without a personal or family history of paraganglioma had germline mutations in SDHB or SDHC. WT GISTs lacking somatic mutations or deletions in SDH subunits had either complete loss of or substantial reduction in SDHB protein expression, whereas most KIT mutant GISTs had strong SDHB expression. Complex II activity was substantially decreased in WT GISTs. WT GISTs, particularly those in younger patients, have defects in SDH mitochondrial complex II, and in a subset of these patients, GIST seems to arise from germline-inactivating SDH mutations. Testing for germline mutations in SDH is recommended in patients with WT GIST. These findings highlight a potential central role of SDH dysregulation in WT GIST oncogenesis.