Multiple heterochronic gastrointestinal stromal tumors in the stomach detected 6 years after resection: a case report.

Background: To date, only a few cases of multiple GISTs with different clones in different organs have been published. However, a case of multiple GISTs with different clones occurring in a single organ has never been reported.

Case Presentation: A 41-year-old patient underwent laparoscopic partial gastrectomy for gastric gastrointestinal stromal tumor (GIST) in 2012. The pathological findings showed high-risk characteristics for recurrence, so he received adjuvant therapy with imatinib for 3 years. In 2018, 3 years after completing the adjuvant therapy, tumor lesions at residual gastric cardia were incidentally identified by follow-up computed tomography (CT). The pathological findings of the tumor biopsy revealed gastric GIST. He underwent secondary laparoscopic partial gastrectomy and was diagnosed with high-risk GIST. Adjuvant therapy with imatinib was restarted immediately. The two gastric GISTs had the same exon 11 mutations in the c-kit gene, but they had different missense mutations. This molecular heterogeneity suggested that they were derived from different origins.

Conclusion: We reported a multiple heterochronic GIST in the stomach detected 6 years after resection. There may be a possibility that another heterochronic GIST will occur in the remnant stomach in the future, so close follow-up will be needed.