Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 8 4 2024 01 10 159 162 Faraz Mahdizadeh Students Research Committee, School of medicine, Ardabil University of Medical Sciences, Ardabil, Iran Mir Mehdi Chinifroush-Asl Department of Pathology, School of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran Farzad Heidary Students Research Committee, School of medicine, Ardabil University of Medical Sciences, Ardabil, Iran 2023 08 24 2023 10 24 Colorectal cancer affects the rectum or large bowel, including the appendix. This type of cancer develops from the colorectal mucosa, with adenocarcinoma being the most common form, accounting for over 95% of cases. It typically affects individuals aged 50 years or older. However, this report highlights a case of colorectal adenocarcinoma that occurred at a young age, despite no family history. Unfortunately, the cancer was initially missed during check-ups because of the unlikely age group, resulting in a delayed diagnosis. The patient, who presented with an obstruction, underwent surgical interventions. Upon further examination, the histopathological tests revealed that the patient had well-differentiated type I colorectal adenocarcinoma. https://crcp.tums.ac.ir/index.php/crcp/article/view/864