Recurrence of a small gastric gastrointestinal stromal tumor with high mitotic index
Accepted for publication April 10, 2018
Correspondence Keith M Skubitz, MD; skubi001@umn.edu
Disclosures The authors report no disclosures/conflicts of interest.
Citation JCSO 2018;16(3):e163-e166.
©2018 Frontline Medical Communications
doi https://doi.org/10.12788/jcso.0402
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Discussion
Small gastric GISTs are sometimes found by endoscopy performed for unrelated reasons. Recent data suggest that the incidence of gastric GIST may be higher than previously thought. In a Japanese study of patients with gastric cancer in which 100 stomachs were systematically examined pathologically, 50 microscopic GISTs were found in 35 patients.28 Most small gastric GISTs have a low mitotic index. Few cases have been described with a high mitotic index. In a study of 1765 cases of GIST of the stomach, 8 patients had a tumor size less than 2 cm and a mitotic index greater than 5. Of those, only 6 patients had long-term follow-up, and 3 were alive without disease at 2, 17, and 20 years of follow-up.7 These limited data make it impossible to predict outcomes in patients with small gastric GIST with a high mitotic index.
For patients who are at high risk of recurrence after surgery, 3 years of adjuvant imatinib treatment compared with 1 year has been shown to improve overall survival and is the current standard of care.10,17 A study comparing 5 and 3 years of imatinib is ongoing to establish whether a longer period of adjuvant treatment is warranted. In patients with metastatic GIST, lifelong imatinib until lack of benefit is considered optimal treatment.10 All patients should undergo KIT mutation analysis. Those with the PDGFRA D842V mutation, SDH (succinate dehydrogenase) deficiency, or neurofibromatosis-related GIST should not receive adjuvant imatinib.
This case has several unusual features. The small tumor size with a very high mitotic rate is rare. Such cases have not been reported in large numbers and have therefore not been reliably incorporated into risk prediction algorithms. In addition, despite a high mitotic index, the tumor was not FDG avid on PET imaging. The diagnosis of GIST is strongly supported by the KIT mutation and response to imatinib. This particular KIT mutation in larger GISTs is associated with aggressive disease. The present case adds to the data on the biology of small gastric GISTs with a high mitotic index and suggests the mitotic index in these tumors may be a more important predictor than size.
,Acknowledgment
The authors thank Michael Franklin, MS, for editorial assistance, and Sabrina Porter for media edits.
