Careful Interpretation of Positron Emission Tomography Findings in Gastric Schwannomas: A Case Report.

Positron emission tomography (PET) is a valuable tool for determining whether tumors are benign or malignant; however, it may occasionally lead to overdiagnosis or underdiagnosis. A 39-year-old woman was incidentally detected with her gastric mass and regional lymph node swelling on computed tomography (CT). Gastro-endoscopy showed a submucosal tumor protruding into the gastric lumen with two overlying ulcers. PET showed a maximal standard uptake (SUVmax) value of 11 in the submucosal gastric tumor but no uptake in the enlarged regional lymph nodes. Despite the absence of malignant cells in the biopsy specimen, the large tumor size, protruding growth pattern into the gastric lumen, avid radiotracer uptake, regional lymph node swelling, and the patient's young age led us to treat the gastric submucosal tumor not with tumorectomy, but with distal gastrectomy followed by D1 lymphadenectomy to avoid undertreatment. Postoperative pathological study showed that the gastric tumor was an Antoni A-type schwannoma, had intra-tumoral infection, and had no malignant findings in the dissected regional lymph nodes. Physicians should note that gastric schwannoma can have a high SUVmax value and may be overevaluated as a possible malignancy.