An unusual cause of hemorrhagic shock in a 14-year-old child.

A 14-year-old girl underwent colonoscopy due to repeated flesh-washing watery stools and dull pain around the umbilicus for 10 days. She felt tired for 1 month with no other significant discomfort. The hemoglobin (Hb) is 66g/L, and the red blood cell (RBC) count was 3.24*10^12/L in routine blood tests at admission. Abdominal computed tomography (CT) images showed submucosal tumor (SMT) in the descending colon. The abdominal computed tomography (CT) images showed submucosal tumor (SMT) in the descending colon. The SMT, supplied by the superior and inferior mesenteric arteries, showed significant enhancement at the arterial stage. It did not reveal any bowel wall thickening, enlarged lymph nodes, or ascites, suggesting that the SMT was probably a benign submucosal lesion. The submucosal tumor lesion measured in size 25*25mm located at the descending colon. Endoscopic ultrasonography imaging showed a mixed hyperechoic with a regular edge, originating from the submucosa and closely related to the muscularis propria. There were no evident features of malignancy or metastasis. Endoscopic full-thickness resection (EFR) was carried out for en bloc resection. The tumor was located in the submucosa with a clear boundary and intact capsule. The tumor cells exhibited acinar and nested patterns with abundant thin-walled blood vessels. These tumor cells were epithelioid, displaying abundant clear or eosinophilic cytoplasm. The nuclei were round or oval. Immunohistochemical analysis revealed that the tumor cells showed positive staining for HMB-45 and TFE3, but were negative for SMA.