S4004 Rising Concerns: A Case of YO-CRC in a 24-Year-Old Male

Introduction: Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second leading cause of cancer-related deaths worldwide. CRC incidence has stabilized or declined in high-income countries due to screening in individuals aged 45 and older, there has been a concerning rise in younger populations, termed young-onset colorectal cancer (YO-CRC), which refers to cases diagnosed before age 50. By 2030, YO-CRC is projected to comprise 11% of colon cancer and 23% of rectal cancer diagnoses. This trend suggests a strong birth cohort effect, implicating environmental and lifestyle changes as key contributors. This case report highlights the importance of maintaining a high index of suspicion for CRC in younger patients. Case Description/Methods: We present a 24-year-old man with no significant prior medical history who presented to the Emergency Department with unintentional weight loss, abdominal pain, nausea, vomiting, constipation, and malaise over 3 months. Computed tomography revealed a large cecal mass with extensive mesenteric adenopathy. No family history of CRC. Lab studies showed iron-deficiency anemia and elevated CRP, while tumor markers were unremarkable. Colonoscopy found a partially obstructing cecal mass, and biopsy indicated moderately differentiated invasive adenocarcinoma. Immunostaining revealed loss of MLH1 and PMS2 proteins, suggestive of mismatch repair deficiency. Genetic analysis showed no mutations in NRAS or BRAF, indicating a diagnosis of Lynch Syndrome (LS). Discussion: LS, resulting from mutations in DNA mismatch repair genes, typically presents CRC at ages 44 to 61. Our patient’s diagnosis at age 24 is notably early. Absence of BRAF mutations and loss of MLH1 and PMS2 support this diagnosis. Emerging evidence suggests that environmental factors and dietary patterns may contribute to the rising incidence of YO-CRC, including high red meat consumption, low fiber intake, and early-life exposures. Disparities in incidence rates have also been observed among different ethnic groups. The increasing rates of YO-CRC have prompted guideline changes, recommending average-risk screening starting at age 45. However, many YO-CRC patients are diagnosed earlier, necessitating tailored even earlier screening strategies. Our case emphasizes the need for heightened clinical suspicion in young patients presenting with GI symptoms and highlights the importance of earlier diagnostic workup and further research into YO-CRC's molecular mechanisms for improved patient outcomes. As well as the rise of YO-CRC which may again support the need to start CRC earlier than 45.