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Stages and Symptoms of Colon Cancer
The earliest system to identify the various colon cancer stages and symptoms is the Dukes Classification that grouped the patients into three categories (Stage A,B,C) before Astler-Coller introduced a Stage D for distant spread of cancer.
The American Joint Committee on Cancer (AJCC) has introduced the TNM staging system, a most commonly used method to identify colon cancer stages and symptoms these days.
The TNM staging system is one of the widely used staging systems for cancer reporting. TNM system is based essentially on the following principles:
Extent of Tumor (T)
Tis: The earliest stage (in situ) of tumor involving only the mucosa.
T1: Tumor invades submucosa.
T2: Tumor invades muscularis propria.
T3: Tumor invades through the muscularis propria into the subserosa, or into the pericolic or perirectal tissues.
T4: Tumor directly invades other organs or structures, and/or perforates.
Extent of Spread to Lymph Node (N)
N0: No regional lymph node metastasis.
N1: Metastasis in 1 to 3 regional lymph nodes.
N2: Metastasis in 4 or more regional lymph nodes.
Presence or Absence of Distant Metastasis (M)
M0: No distant metastasis.
M1: Distant metastasis present.
Thus, T2 N0 M0 in colon cancer means that the tumor is located only in the muscle and has not spread to the lymph nodes or any other part of the body.
Though TNM combinations correspond to one of five stages, criteria for stages is type specific, differ for different types of cancer.
Stage 0: Tis N0 M0 Earliest stage of cancer. It has not grown beyond the inner layer (mucosa) of the colon or rectum. This stage is also known as carcinoma in situ or intramucosal carcinoma.
Stage I: T1 N0 M0; T2 N0 M0
Cancer has begun to spread, but is still in the inner lining.
Stage II: T3 N0 M0; T4 N0 M0
Cancer has spread to other organs near the colon or rectum. It has not reached lymph nodes.
Stage III: any T, N1-2, M0
Cancer has spread to lymph nodes, but has not been carried to distant parts of the body.
Stage IV: any T, any N, M1
Cancer has been carried through the lymph system to distant parts of the body. This is known as metastasis. The most likely organs to experience metastasis from colorectal cancer are the lungs and liver.
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Symptoms of Colon Cancer
In view of the slow growing nature of the cancer, it takes quite a long period of time for patients to present with symptoms. The symptoms of colon cancer depend much on:
Site of Cancer:
The right ascending colon has a larger lumen with a thin wall carrying liquid content as compared to the left descending colon which has a narrower lumen and thick wall carrying semi solid content. Due to these differences, obstruction due cancer of the right colon occurs at later stage of disease though the patient may just have complaints of giddiness, fatigue as a result of iron deficiency anemia.
Tumors commonly encircle the left colon, leading to alternating constipation and frequent bowel movement. It is important to know that rectal cancer may present as hemorrhoids or diverticular disease. Thus, bleeding during bowel emptying must be investigated for cancer.
Sometimes, the patient also complains of incomplete emptying of the bowel and associated with painful bowel movement which may suggest the tumor may have involved surrounding tissues.
Extent of the Cancer:
Once the cancer has spread beyond the colon, then the patient may develop symptoms related to the affected systems. Liver involvement may present with yellowish discoloration of the eye (jaundice), progressive abdominal distension and swelling of the legs. Chronic coughing and breathlessness could be a clue for metastasis to the lungs.
General systemic symptoms could be unexplained loss of weight and loss of appetite coupled with excessive fatigue and pale looking appearance.
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1. Characteristics of colon cancer at time of presentation. Stein W, Farina A, Gaffney K, Lundeen C, Wagner K, Wachtel T. Department of Community Health, Brown University School of Medicine, Providence, RI
2. Colorectal Cancer Staging, What is it? Why is it needed? A Cancer Journal for Clinicians
3. Myths about Colon Cancer. American Cancer Society