Stages of Colon Cancer
Colorectal carcinoma is one of the most common neoplasms in people over 50 years of age. It usually has a favorable prognosis in most cases, especially when it’s detected in the initial stages. However, the most advanced stages of colon cancer have a much shorter life expectancy, requiring palliative care.
Colon cancer staging can be done based on the Dukes classification or TNM. Studies establish that the most widely used classification internationally is the second, because it offers more detailed information.
Stages of colon cancer according to the TNM classification
The TNM classification was established by the American Joint Committee on Cancer (AJCC). It takes into account the invasion of the tumor in the intestinal wall, the involvement of lymph nodes, and the presence of metastases. All these categories have sub-classifications.
The different stages of colon cancer can only be identified after multiple tests, with colonoscopy being one of the most important. It allows a sample of the lesion to be taken for a biopsy.
Tumor invasion (T)
The large intestine is made up of multiple cell layers, which have their own characteristics and allow the proper functioning of the organs. Generally speaking, the colon has a mucous layer, a submucosa, a muscularis propria, a subserosa, and a serosa (from the inside out).
The letter T of the classification refers to the ability of the tumor to invade each of the layers of the intestine. The tumors usually start in the mucosa. However, they’re able to invade more and worsen the symptoms.
In this way, the stages of colon cancer in terms of tumor invasion are as follows:
- Tx: when the primary tumor cannot be evaluated.
- T0: used when there’s no evidence of a tumor in the colon.
- Tis: this refers to the presence of a carcinoma in situ. In this sense, the tumor is confined to the mucous layer of the colon.
- T1: at this point, the tumor increased in depth, affecting even the submucosal layer.
- T2: Cancer invades the muscularis propria layer of the intestine.
- T3: This is any neoplasm that came to invade the subserous layer of the intestine. It also refers to the fact that the tumor has invaded the perirectal fatty tissue.
- T4a: The cancer has affected the fatty tissue around the colon, called the peritoneum.
- T4b: It has spread and affected other nearby abdominal organs.
Lymph node involvement (N)
The letter N in the classification refers to the presence of cancer cells in the abdominal lymph nodes near the tumor. Lymph nodes are small organs that are found throughout the body.
Many types of cancer have the ability to spread throughout the lymphatic system, which can cause swollen glands. Their affection is of vital importance when determining the treatment of colon cancer, since it’s synonymous with advanced stages.
In this sense, it can be classified as follows:
- Nx: The abdominal lymph nodes near the injury can’t be assessed.
- N0: This refers to the absence of cancer cells in the lymph nodes.
- N1: The cancer has spread through the lymphatic system, affecting between 1 and 3 nodes.
- N2: The spread of the cancer is greater, and can be found in up to more than 4 lymph nodes.
Metastasis (M)
Metastasis refers to the ability of different types of cancer to spread to distant lymph nodes or other organs. This characteristic is present in the most serious stages of colon cancer, thus reducing life expectancy.
It’s only possible to divide it into 2 categories:
- M0: When there’s no metastasis.
- M1: Indicates involvement of distant lymph nodes or other abdominal organs.
Colon cancer stages
All subcategories of the TNM classification are combined to produce the final stage of the disease. This situation is very similar to what happens with the stages of breast cancer and other oncological diseases.
It is possible to find the following stages:
- Stage 0: This indicates the presence of a carcinoma in situ, that is, a tumor confined to the mucosa layer.
- Stage I: This is a tumor that hasn’t penetrated the muscular layer of the intestine, without lymph node involvement or metastasis.
- Stage II: This refers to a tumor that has invaded all layers of the intestine, without lymph node involvement or metastasis. This stage can be divided into IIa, when there’s a T3 tumor, or IIb when a T4 tumor is present.
- Stage III: This is a tumor of variable size, which has spread to nearby lymph nodes without metastasizing. It can be divided into IIIa in the case of a T1 or T2 tumor and N1 or IIIb when it’s a T3 or T4 and N1 tumor. Lastly, stage IIIc is present when 4 or more lymph nodes are affected.
- Stage IV: This refers to any tumor that has metastasized.
The staging of tumors is of vital importance in establishing the prognosis. In this sense, life expectancy is better in the early stages of colon cancer. Studies determine that 67% of people with T1 or T2 tumors survive more than 5 years after diagnosis.
Stages of colon cancer according to the Dukes classification
This classification is also known as the Aster and Coller classification. It evaluates the tumor, depending on the same characteristics as the TNM classification. However, it’s less accurate, so its use has decreased over the years.
The Dukes classification uses the use of letters, A through D. The stages are slightly simpler, making it easier for people to understand the severity of their condition.
Among the different stages of colon cancer according to the Dukes classification are the following:
- Stage A: A tumor limited to the mucosa without lymph node involvement, that is, a carcinoma in situ.
- Stage B1: The cancer penetrates beyond the mucous layer, without affecting the entire intestinal wall and without lymphatic spread.
- Stage B2: This is a tumor that affects the wall throughout its thickness, without lymphatic invasion.
- Stage C: The main characteristic of this stage is the involvement of the abdominal lymph nodes.
- Stage D: This refers to all colon cancer that has affected distant organs.
Early diagnosis is essential
The different stages of colon cancer let specialist doctors know how advanced the disease is. This information is essential in order to determine the correct treatment.
The initial stages of colon cancer have a high probability of cure. In this sense, it’s essential to assist the doctor when suffering from any abnormal symptoms that indicate the presence of colon cancer or some other gastrointestinal pathology.
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