Colon Adenocarcinoma Location and Distribution

Primary Tumor Distribution

• Left-sided tumors (distal to splenic flexure) comprise approximately 75% of obstructing colorectal cancers, with the sigmoid colon being the most common location, according to the World Journal of Emergency Surgery and supported by other guidelines 1, 2

Right Colon vs. Left Colon Distribution

• Right colon tumors (cecum, ascending colon, proximal transverse colon) account for approximately 10-20% of colon cancers, as reported by the Annals of Oncology 3
• Malignant polyps show a bimodal distribution: most commonly in the sigmoid colon (52.6% of malignant polyps), followed by the rectum (35.3%), with the right colon accounting for 17.9%, according to Gastroenterology 4, 5

Clinical Implications by Location

• Sigmoid location is associated with the highest risk of obstruction, as this is the narrowest portion of the colon with the most formed stool, as noted by the World Journal of Emergency Surgery 1

Geographic Variations

• In the Middle East and North Africa region, the rectum is the most common primary site (42.5%), followed by the sigmoid colon (23.2%), which differs from Western patterns, as reported by the Journal of the National Comprehensive Cancer Network 6, 7, 8

Practical Clinical Approach

• Complete colonoscopy is essential because approximately 35% of tumors occur proximal to the sigmoid colon, and synchronous lesions occur in 2.5% of cases, necessitating complete colonic visualization, according to the Annals of Oncology 3