Recent changes in the USPSTF guidelines recommend that CRC (Colorectal Cancer) screening in average-risk patients should commence at 45 years with the intent of finding sporadic premalignant or malignant polyps, allowing early endoscopic interventions to improve clinical outcomes. This study aims to find the incidence of sporadic malignant polyps in adult patients < 50 years of age) from the National Cancer Institute's SEER (Surveillance Epidemiology and End Results) database over a period of 18 years.


We interrogated the SEER database (2000-2017) on patients aged 20-49 years diagnosed with at least a single malignant sporadic colorectal polyp. Data extraction was performed through a case listing session using SEER*Stat v8.3.9 on combined SEER 18 incidence registries using specific codes for CRC polyps with cancer (Table). Microsatellite instability (MSI-H) high lesions and adenomatous polyposis coli (APC) were excluded from the analysis. Descriptive statistical analysis was performed using SPSS v27 for Mac.


A total of 10,742 patients with a diagnosis of colorectal polyps with a malignant component were identified. Female patients comprised 42.9% of the cohort with a mean age of any malignant polyp incidence of 43.07 years (42.91-43.23, 95% CI). The annual mean age (95% CI) of incidence of new-onset malignant polyps over time is shown in Figure 1. Approximately 50% of malignant polyps were diagnosed between 45-49 years of age, and about 25-30% were diagnosed between 40-45 years of age (Table). The incidence of malignant villous adenomas decreased, whereas malignant adenomas and tubulovillous adenomas increased over time (Table). A rising temporal trend for the total number of patients diagnosed with malignant polyps was also observed. Serrated polyps with cancer were noted to be scarce in the population studied.


Our results show the mean age of sporadic malignant colorectal polyp incidence occurrence at 43 years. Approximately half of the malignant polyps under age 50 occurred in patients under age 45, below the current screening threshold of 45 years. Also observed was a temporal change in the histological patterns of colorectal malignant polyps, with malignant tubulovillous and adenomatous adenomas increasing and villous adenomas decreasing with the scarcity of serrated polyps with cancer in this population. These results have profound implications for colorectal cancer screening.

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The American Journal of Gastroenterology