A 12-year-old boy with severe periumbilical pain visited the emergency room. Physical examination, abdominal ultrasonography, colonoscopy and CT, identified a lesion of sigmoid colon. Endoscopic biopsy showed a signet ring cell carcinoma of the sigmoid colon. On explorative laparotomy, cancer invasions of the adjacent structures and metastases on peritoneal wall were noticed. We performed palliative loop-ileostomy. He underwent chemotherapy and radiotherapy for 3 months. The second case was a 16-year-old boy with abdominal pain and hematochezia, transferred to our hospital with the diagnosis of acute appendicitis with periappendiceal abscess. Although he underwent appendectomy, the abdominal pain persisted. Digital rectal examination revealed a lumen-obstructing fungating mass in the rectum. Endoscopic biopsy revealed a adenocarcinoma. Cancer invasion of the adjacent structures and metastases involving the mesentery of the small intestine were found at laparotomy. A palliative procedure, a Hartmann's operation and end-colostomy at the sigmoid colon were performed. The patient died 8 month later due to pneumonia and sepsis. Chemotherapy was not applied.
