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Colorectal cancer (CRC) is one of the leading causes of cancer related mortality worldwide. Although young-onset CRC raises the possibility of a hereditary component, hereditary CRC syndromes only explain a minority of young-onset CRC cases. There is evidence to suggest that young-onset CRC have a different molecular profile than late-onset CRC. While the pathogenesis of young-onset CRC is well characterized in individuals with an inherited CRC syndrome, knowledge regarding the molecular features of sporadic young-onset CRC is limited. Understanding the molecular mechanisms of young-onset CRC can help us tailor specific screening and management strategies. While the incidence of late-onset CRC has been decreasing, mainly attributed to an increase in CRC screening, the incidence of young-onset CRC is increasing. Differences in the molecular biology of these tumors and low suspicion of CRC in young symptomatic individuals, may be possible explanations. Currently there is no evidence that supports that screening of average risk individuals less than 50 years of age will translate into early detection or increased survival. However, increasing understanding of the underlying molecular mechanisms of young-onset CRC could help us tailor specific screening and management strategies. The purpose of this review is to evaluate the current knowledge about young-onset CRC, its clinicopathologic features, and the newly recognized molecular alterations involved in tumor progression.

Juvenile polyps are relatively common findings in children, while juvenile polyposis syndrome (JPS) is a rare hereditary syndrome entailing an increased risk of colorectal cancer. Mutations in BMPR1A or SMAD4 are found in roughly half of patients diagnosed with JPS. Mutations in PTEN gene are also found in patients with juvenile polyps and in Bannayan-Riley-Ruvalcaba syndrome and Cowden syndrome. Several previous reports have described microdeletions in chromosome 10q23 encompassing both PTEN and BMPR1A causing aggressive polyposis and malignancy in childhood. These reports have also described extra-intestinal findings in most cases including cardiac anomalies, developmental delay and macrocephaly. In this report we describe a boy with a 5.75 Mb deletion of chromosome 10q23 and a 1.03 Mb deletion within chromosome band 1p31.3 who displayed aggressive juvenile polyposis and multiple extra-intestinal anomalies including macrocephaly, developmental delay, short stature, hypothyroidism, atrial septal defect, ventricular septal defect and hypospadias. He required colectomy at six years of age, and early colectomy was a common outcome in other children with similar deletions. Due to the aggressive polyposis and reports of dysplasia and even malignancy at a young age, we propose aggressive gastrointestinal surveillance in children with 10q23 microdeletions encompassing the BMPR1A and PTEN genes to include both the upper and lower gastrointestinal tracts, and also include a flowchart for an effective genetic testing strategy in children with juvenile polyposis.