[Intermittent abdominal pain and abdominal distension with fatigue and massive ascites in a 13-year-old boy].

A 13-year-old boy was admitted due to intermittent abdominal pain for one year with massive ascites. The purified protein derivative (PPD) test after admission yielded positive results (3+), and ascites examination revealed a yellow color. There were 634×10⁹ nucleated cells/L in the ascites, among which 82.2% were mononuclear cells and 17.8% were multinuclear cells. The Rivalta test yielded a positive result and revealed that the ascites was exudate, suggesting the possibility of tuberculosis infection. The symptoms were not relieved after isoniazid-rifampicin anti-tuberculosis therapy and symptomatic/supportive treatment. Plain CT scan of the abdomen and contrast-enhanced CT showed that the lesion was located at the left wall of the transverse colon, with uneven thickening of the peritoneum and heterogeneous enhancement. Colonoscopic biopsy found signet ring cells in the mucosa and immunohistochemical examination revealed Syn (-), CgA (-), CD56 (-), CK(pan) (+), CDX-2 (+), CK20 (+), Muc-1 (+) and Ki-67 (+, about 80%). PET-CT scan showed an abnormal increase in fluorodeoxyglucose metabolism, which was shown as a mass near the splenic flexure of the transverse colon, with a maximum standard uptake value of 9.9, indicating a highly active lesion; this was consistent with the metabolic changes of malignant tumors. Surgical operation was performed and intraoperative exploration revealed massive ascites, a hard mass located at the hepatic flexure of the colon, involvement of the serous coat and surrounding tissues, stenosis of the bowel, lymph node enlargement around the superior mesenteric vessels and the gastrocolic ligament, and multiple metastatic nodules in the greater omentum, the abdominal wall and the pelvic cavity. The results of postoperative pathology were consistent with those of colonoscopic biopsy, i.e., poorly differentiated mucinous adenocarcinoma of the transverse colon and partly signet-ring cell carcinoma. Therefore, the boy was diagnosed with colon signet-ring cell carcinoma with peritoneal metastasis and tuberculosis infection. When a child is suffering from intractable abdominal pain, unexplained intestinal obstruction and massive intractable ascites, the possibility of malignancy should be considered. Abdominal plain CT scan as well as contrast-enhanced CT scan should be performed as early as possible, and enteroscopy should be performed when necessary.