Ileocecal intussusception secondary to poorly differentiated mucinous adenocarcinoma with focal signet ring cell component in a 15-year-old adolescent: a case report

Intussusception in adolescents is uncommon and more frequently associated with a pathological lead point than in infants and young children. Pediatric colorectal adenocarcinoma is exceedingly rare, and poorly differentiated mucinous adenocarcinoma with signet ring cell differentiation is particularly aggressive. We report a rare adolescent case presenting as ileocecal intussusception and highlight key diagnostic implications. Case presentation: We report a 15-year-old boy who presented with intermittent abdominal pain for 10 days. Computed tomography revealed ileocecal intussusception, which was successfully reduced by pneumatic enema. Post-reduction ultrasonography identified a suspicious lesion in the ascending colon. Subsequent colonoscopy revealed a broad-based, firm, mucus-covered mass in the ascending colon near the ileocecal valve, and biopsy confirmed poorly differentiated mucinous adenocarcinoma with a focal signet ring cell component. The patient underwent right hemicolectomy with lymphadenectomy. Final pathology revealed pT3N2aM0 disease (AJCC 8th edition, stage IIIB) with retained mismatch repair protein expression, suggesting microsatellite stability. The patient received adjuvant CAPOX chemotherapy and remains disease-free at 7-month follow-up. Successful reduction of adolescent intussusception should not end the diagnostic workup. Systematic post-reduction evaluation is essential to identify a pathological lead point, and normal tumor markers should not provide false reassurance. Timely tissue diagnosis and multidisciplinary oncologic management are critical.