Colon cancer, also known as colorectal cancer when it involves both the colon and rectum, is a type of cancer that begins in the large intestine, which is the final part of the digestive tract. It usually starts as small, noncancerous clumps of cells called polyps that form on the inner lining of the colon or rectum. Over time, some of these polyps can develop into cancer. The most common type of colon cancer is adenocarcinoma, accounting for about 95% of cases, which originates from the glandular cells lining the colon[1].
The colon is a muscular tube that absorbs water and nutrients from food and stores waste before it is eliminated. When cancer develops here, it can interfere with these functions and cause various symptoms. However, colon cancer often does not cause symptoms in its early stages, which is why screening is crucial for early detection[1].
Symptoms of colon cancer can vary depending on the location of the tumor within the colon. The colon is divided into sections: the right side (including the cecum, ascending colon, and transverse colon) and the left side (including the splenic flexure, descending colon, sigmoid colon, and rectosigmoid junction). Right-sided colon cancers often cause occult bleeding (hidden blood loss) leading to iron deficiency anemia, which may present as fatigue or weakness. They may also cause melena (black, tarry stools) or diarrhea[1]. Left-sided colon cancers tend to cause changes in bowel habits such as constipation or diarrhea, blood-streaked stools, and colicky abdominal pain due to obstruction, as the left colon has a narrower lumen and solid stool[1].
Common symptoms that should raise suspicion for colon cancer include:
– Persistent changes in bowel habits (diarrhea, constipation, or narrowing of stool)
– Blood in the stool or rectal bleeding
– Unexplained weight loss
– Unexplained iron deficiency anemia, especially in men over 50 and postmenopausal women
– Abdominal discomfort or cramps
– Fatigue
– Bloating or abdominal pain
– Nausea or vomiting
– Bowel obstruction symptoms such as severe abdominal pain and inability to pass stool or gas[1][2][3][4]
Rectal bleeding is a particularly important symptom, especially in younger adults under 50, where it has been linked to an 8.5 times higher risk of early-onset colorectal cancer. Many young patients with colorectal cancer do not have a family history of the disease, and symptoms are often the reason for diagnosis rather than routine screening[5].
Colon cancer is staged based on how far it has spread. The staging system ranges from stage 0 (very early cancer confined to the inner lining) to stage 4 (cancer that has spread to distant organs). Stage 3 colon cancer means the cancer has spread through the colon wall and reached nearby lymph nodes but has not spread to distant organs. It is subdivided into IIIA, IIIB, and IIIC depending on the depth of invasion and number of lymph nodes involved[2].
Diagnosis of colon cancer typically involves a colonoscopy, which allows direct visualization of the colon and biopsy of suspicious lesions. Once cancer is confirmed, imaging tests such as CT scans are used to determine the stage and guide treatment[1].
Treatment depends on the stage and may include surgery to remove the tumor, chemotherapy, radiation therapy, or combinations of these. Early-stage cancers may be treated with surgery alone, while advanced stages often require systemic therapies. Even stage 4 colon cancer, where the disease has spread to other parts of the body, can sometimes be managed with targeted therapies and clinical trials offering hope for improved outcomes[4].
Because early colon cancer often causes no symptoms, regular screening is recommended starting at age 45 or earlier for those with risk factors such as family history, certain genetic conditions, or lifestyle factors like smoking. Screening methods include colonoscopy, stool tests, and imaging studies. Early detection significantly improves survival rates and reduces the need for aggressive treatments[1][3].
In summary, colon cancer is a common and potentially serious disease that arises from the lining of the large intestine. It often begins silently but can cause symptoms related to bleeding, bowel changes, and obstruction as it progresses. Awareness of symptoms, risk factors, and adherence to screening guidelines are essential for early diagnosis and effective treatment.
Sources:
[1] AMBOSS – Colorectal cancer
[2] AdventHealth – 3 Things to Know About Stage 3 Colorectal Cancer
[3] Everhope Care – Colon Cancer Symptoms to Never Ignore
[4] Hirschfeld Oncology – Stage 4 Colon Cancer
[5] Healthline – Rectal Bleeding in Young Adults Linked to Higher Risk of Colorectal Cancer
