Introduction and importance: Colorectal cancer (CRC) in children represents less than 1% of pediatric malignancies worldwide. Signet-ring cell carcinoma (SC), a subtype associated with mucin-producing phenotypes and distinct molecular pathways, is infrequently encountered in this age group, particularly in low-resource settings. Presentation of case: A 10-year-old boy presented with 1 month of right lower quadrant pain, progressive abdominal distension, anorexia, constipation, and weight loss. Radiologic studies (plain abdominal X-ray, barium enema, and CT scan) showed right-sided colonic obstruction with secondary compression of the duodenum and gallbladder, initially raising suspicion of congenital duodenal bands. Laparotomy identified obstructing mass at the hepatic flexure. Right hemicolectomy was performed. Histology confirmed poorly differentiated SC (pT4a N2b M0) with extensive lymphovascular invasion. Immunohistochemistry indicated mismatch repair proficiency. Clinical discussion: Pediatric SC CRC is only sparsely reported, and available data suggest distinct biological characteristics. The tumor’s diffuse infiltrative pattern is typically driven by intracellular mucin accumulation that displaces the nucleus, loss or reduction of E-cadherin–mediated cell adhesion, and activation of epithelial–mesenchymal transition pathways. Mismatch repair stability, as observed in this case, points toward non–MMR-driven oncogenesis, indicating a carcinogenic pathway independent of Lynch syndrome or sporadic MSI-high mechanisms. MMR-stable early-onset tumors may develop via chromosomal instability, epigenetic promoter methylation, or Wnt/β-catenin signaling activation. Conclusion: This case illustrates the complex molecular features characterizing signet-ring cell colorectal carcinoma in young patients reinforcing the need for heightened diagnostic vigilance and further region-specific studies to better delineate the underlying biology of early-onset CRC in resource-limited settings.
Leal et al. (Thu,) studied this question.