Composite gangliocytomaeuroma and neuroendocrine tumors (CoGNETs) are extremely rare periampullary neoplasms composed of neuroendocrine epithelial, Schwannian spindle, and ganglion cells. Although endoscopic papillectomy or surgery have been used to treat ampullary CoGNETs, underwater endoscopic mucosal resection (UEMR) for periampullary lesions has not been previously described. In this study, we present a case of a 53-year-old man referred to our hospital with an incidentally detected subepithelial tumor in the second portion of the duodenum. Endoscopic ultrasound revealed a 13×10-mm homogeneous, hypoechoic, and well-demarcated submucosal mass. UEMR was performed under conscious sedation without submucosal injection, achieving safe en bloc resection within 12 min. Histopathology revealed a 2.0×1.5×1.2-cm lesion composed of mixed neuroendocrine epithelial, Schwannian spindle, and ganglion cells. Immunohistochemical staining was positive for chromogranin A, synaptophysin, CD56, neuron-specific enolase, and S-100, confirming CoGNET with a Ki-67 index of <1% and no lymphovascular or perineural invasion. Follow-up endoscopy 3 months later revealed only a post-resection scar without residual or recurrent tumors. This appears to be the first reported case of periampullary CoGNET successfully treated with UEMR. Therefore, UEMR might represent a safe and effective therapeutic option for selected periampullary subepithelial tumors.

Adipose-derived stem cells are gaining attention because they are easily obtained in large quantities. However, concerns about side effects of their use have also been raised. Mycobacterial infections can develop during stem cell treatment in the event of incomplete medical device sterilization and/or suboptimal hygiene during cell processing and culture. In general, mycobacterial infections most frequently manifest as pneumonia; however, infections of the bones, lymph nodes, skin, soft tissues, and blood also occur. Mycobacterial bacteremia occurs relatively frequently, but cases of gastric ulcers induced as a complication of stem cell treatment and subsequent mycobacterial bacteremia have not been reported. Herein, we report a 75-year-old man who developed mycobacterial bacteremia and gastric ulcers following adipose-derived stem cell injection. This case report raises awareness of the possibility of Mycobacterium abscessus complex bacteremia and subsequent gastric ulcer bleeding—a rare complication of stem cell therapy.

Adipose-derived stem cells are gaining attention because they are easily obtained in large quantities. However, concerns about side effects of their use have also been raised. Mycobacterial infections can develop during stem cell treatment in the event of incomplete medical device sterilization and/or suboptimal hygiene during cell processing and culture. In general, mycobacterial infections most frequently manifest as pneumonia; however, infections of the bones, lymph nodes, skin, soft tissues, and blood also occur. Mycobacterial bacteremia occurs relatively frequently, but cases of gastric ulcers induced as a complication of stem cell treatment and subsequent mycobacterial bacteremia have not been reported. Herein, we report a 75-year-old man who developed mycobacterial bacteremia and gastric ulcers following adipose-derived stem cell injection. This case report raises awareness of the possibility of Mycobacterium abscessus complex bacteremia and subsequent gastric ulcer bleeding—a rare complication of stem cell therapy.

Adipose-derived stem cells are gaining attention because they are easily obtained in large quantities. However, concerns about side effects of their use have also been raised. Mycobacterial infections can develop during stem cell treatment in the event of incomplete medical device sterilization and/or suboptimal hygiene during cell processing and culture. In general, mycobacterial infections most frequently manifest as pneumonia; however, infections of the bones, lymph nodes, skin, soft tissues, and blood also occur. Mycobacterial bacteremia occurs relatively frequently, but cases of gastric ulcers induced as a complication of stem cell treatment and subsequent mycobacterial bacteremia have not been reported. Herein, we report a 75-year-old man who developed mycobacterial bacteremia and gastric ulcers following adipose-derived stem cell injection. This case report raises awareness of the possibility of Mycobacterium abscessus complex bacteremia and subsequent gastric ulcer bleeding—a rare complication of stem cell therapy.

Adipose-derived stem cells are gaining attention because they are easily obtained in large quantities. However, concerns about side effects of their use have also been raised. Mycobacterial infections can develop during stem cell treatment in the event of incomplete medical device sterilization and/or suboptimal hygiene during cell processing and culture. In general, mycobacterial infections most frequently manifest as pneumonia; however, infections of the bones, lymph nodes, skin, soft tissues, and blood also occur. Mycobacterial bacteremia occurs relatively frequently, but cases of gastric ulcers induced as a complication of stem cell treatment and subsequent mycobacterial bacteremia have not been reported. Herein, we report a 75-year-old man who developed mycobacterial bacteremia and gastric ulcers following adipose-derived stem cell injection. This case report raises awareness of the possibility of Mycobacterium abscessus complex bacteremia and subsequent gastric ulcer bleeding—a rare complication of stem cell therapy.