[Expression of succinate dehydrogenase subunit protein in succinate dehydrogenase-deficient gastrointestinal stromal...

Objective: To investigate the expression of succinate dehydrogenase complex subunit protein in succinate dehydrogenase-deficient gastrointestinal stromal tumors (SDH-deficient GISTs). Methods: Three hundred fifty-two cases of GISTs were collected from January 2003 to January 2017 at the Affiliated Hospital of Guizhou Medical University and West China Hospital of Sichuan University.The expression of succinate dehydrogenase subunit protein was detected by immunohistochemical EnVision technique in 352 cases of GISTs, and the negative cases were analyzed for clinicopathologic features and outcome. The gene segments of CKIT exons 9, 11, 13 and 17 and PDGFRA exons 12 and 18 were amplified and detected in SDH-deficient (negative) cases. Results: A total of 15 SDHB-deficient (negative) GISTs (4.3%, 15/352) were found among 352 cases of GISTs. Six patients were male and nine were female. The age of initial diagnosis ranged from 15 to 84 years (median=53 years, mean=47 years). The tumor involved stomach (14 cases) and mesentery (1 case). The tumor sizes varied from 0.5 cm to 15.0 cm (mean=6.9 cm). There were six, six and three cases of epithelioid, mixed and spindle cell types respectively. Eight cases showed multi-nodularity in the wall of stomach. Metastasis to lymph node was noted in four cases, one case showed intraperitoneal implantation metastasis. Metastases to liver, pancreas and lymph node were found in one case, and one case showed vascular invasion. Among SDHB-deficient GISTs, two SDHA-deficient (negative) cases were found (0.6%, 2/352), but there were no SDHC and SDHD deficient (negative) cases. Five of the fifteen SDH-deficient GISTs had follow-up data: one patient died 8 months after surgery from unknown cause, four had no recurrences or metastases, and there was no history of paraganglioma and pulmonary chondroma found in patients and their families. No mutation in CKIT and PDGFRA gene was identified in 15 cases of SDH-deficient GISTs. Conclusion: SDH-deficient GISTs have unique clinicopathologic features and a favorable prognosis, and a small proportion of cases are SDHA-deficient.