Gastrointestinal stromal tumors (GISTs) that are not driven by kinase mutations, as are most GISTs, often show loss of function of the succinate dehydrogenase (SDH) complex and are considered SDH-deficient GISTs. SDH-deficient GISTs share many distinct characteristics compared with conventional GISTs. However, data regarding these characteristics, particularly among Asian people, are relatively limited. The objective of this study was to characterize the clinicopathologic characteristics, treatment, and prognosis of these uncommon GISTs.This retrospective observational study enrolled 12 patients with SDH-deficient GISTs, who were selected from 335 patients with GIST diagnosed at our institution between October 31, 2013 and October 31, 2016 by succinate dehydrogenase subunit B staining.There were 8 male and 4 female patients, with a median age of 57 years (range, 21–73 years). Ten patients (83.3%) were diagnosed at or after the age of 40 years and represented 7.2% (10/138) of the entire population of elderly patients with gastric GISTs. The tumor size ranged from 3 to 19 cm (median, 7 cm); the primary tumor was multifocal in 6 cases (50%), and tumors had a multinodular or plexiform architecture in 10 cases (83.3%). Ten cases (83.3%) showed pure epithelioid morphology, with the remaining 2 cases (16.7%) showing mixed histologic subtype. Lymph node metastasis was found at the time of primary resection in 50% (3/6) of patients. Four cases (33.3%) had distant metastasis at presentation. Four patients (33.3%) developed disease progression during imatinib treatment after initial resection, but all of these patients regained disease control when the treatment was altered to sunitinib targeted therapy.SDH-deficient GISTs arise exclusively in the stomach and account for approximately 7.4% (12/162) of gastric GISTs. Moreover, those affecting people older than 40 years are not uncommon and sunitinib may work well for cases showing treatment failure with imatinib.
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