Carcinogenesis is the process by which a normal cell changes to a malignant growth. It can be a slow process that takes place over many years.
Malignant tumours do not have an encapsulated structure so that cells can become detached and be transported in the blood and the lymphatic system. These breakaway cells can form secondary tumours called metastases: the process is called metastasis. Once the tumour has metastasised the cancer is more difficult to treat.
The National Institute for Clinical Excellence (NICE) in the UK states that: “most people diagnosed with advanced colorectal cancer will survive between six and nine months”. Unfortunately, in as many as 80% of cases, patients do not present until the cancer has spread through the bowel wall
Early diagnosis is therefore life saving. The overall survival rate for colorectal cancer is about 40% at 5 years. However if surgery does not achieve at least a 2cm clearance margin on removal of the cancer, the chance of re-occurrence in the next 6 months is over 80%.
Malignant tumours can be divided into the following categories:
• adenocarcinoma
• squamous cell carcinoma
• transitional carcinoma
• basal cell carcinoma
The most common types of tumour in colorectal cancer are adenocarcinomas and squamous cell carcinomas and account for around 95% of all of the types of tumours found in the small and large bowel.
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