Colon cancer is not a single type of cancer.
Its pathogenesis depends on the anatomical location of the tumor and differs between the right and left sides of the colon.
Proximal colon (right side) and distal colon (left side) tumors have different molecular and histological features presented in the table:
Table-Difference between right and left colorectal cancer
| RIGHT COLON | LEFT COLON |
| Right-sided tumors arise from the ascending colon and proximal two-thirds of the transverse colon. | Left-sided tumors arise from the descending and sigmoid colon and a distal third of the transverse colon. |
| They occur in old age. | They occur at a younger age. |
| They predominantly occur in females. | It predominantly occurs in males. |
| They present with mild abdominal pain and anemia-haemorrhagic syndrome. | They present with colicky pain, constipation changes and diarrhea or, obstruction syndrome. |
| Right-sided tumors show sessile serrated adenomas or mucinous adenocarcinomas. Mucinous tumors progress more rapidly than adenomatous polyps and are commonly diagnosed in patients with inflammatory bowel disease. | Left-sided tumors show typical tubular, villous, and adenocarcinoma adenocarcinomas. |
| Right colon cancer has a flat morphology that is difficult to detect by colonoscopy in the early stages of carcinogenesis. | Left-sided tumors have polypoid morphology, they are easier to detect by colonoscopy in the early stages of carcinogenesis. |
| Patients with right colon cancer tend to have more high microsatellite unstable tumors. | Patients with left colon cancer tend to have tumors with high chromosomal instability. |
| T cell infiltration, immunogenicity is high. | Low immunogenicity. |
| They tend to have metastases in the peritoneal region. | They tend to have liver and lung metastases. |
| Better prognosis in the early stages (stage I and II). | The prognosis can be good even in the advanced stages (stage III and IV). |
| They respond well to immunotherapy. | They respond well to adjuvant chemotherapies, including standard chemotherapies and targeted therapies. |