What are the various colorectal cancers?

Colorectal cancers (CRC) are tumors of the rectum and ascending-transverse-descending-sigmoid colon which begin as small polyps and then grow out of control. These cancers are commonly seen in people over the age of 50 years, and in recent years have seen an unprecedented increase likely due to westernization of diet. 

Experts like the Best Oncologist in Lahore recommend yearly screening tests, especially for people with higher risk, for early diagnosis and treatment. Read on to know more about colorectal cancers: its symptoms, types, diagnosis and management.

What is colorectal cancer?

The biggest part of the large intestine is made of colon—which is 1.5 meter long. This includes the ascending, transverse, descending and sigmoid colon. The s-shaped sigmoid colon joins with the rectum, which is then connected to the anus. The function of colon is to absorb water and electrolytes from the remaining food and the rest makes the fecal matter. 

Most of the colorectal cancers begin as small growths on the inside lining of rectum and colon and these growths are referred to as polyps. Over the years, if unchecked, these polys can grow in size and metastasize into cancerous growths. 

There are increased chances of colorectal cancer if:

  • The polyps are larger than 1 cm 
  • There are more than 3 polyps 
  • Pre-malignant condition of dysplasia is seen in the removed polyps. 
  • Other factors like smoking, alcohol, inflammatory bowel disease, family history of colorectal cancer and poor diet. 

If the polyps become cancerous, they grow into the wall of the large bowel, invade the vessels and the lymph nodes and spread to the other organs.   

What are the types of colorectal cancer?

The many types of colorectal cancer include:

  • Adenocarcinomas: these are the most common colorectal cancers that make mucus and lubricate the inside of the large colon. Further sub-types of adenocarcinomas include: mucinous and signet ring tumors. These tumors begin as adenomatous polyps that continue to grow until they turn malignant. Adenocarcinomas can also form in other organs like breast and lung.  
  • Gastrointestinal stromal tumors (GISTs): these stromal tumors begin in the muscular layer of the digestive tract from the interstitial cells of Cajal, as benign growths that later turn cancerous. GISTs can occur anywhere along the digestive tract and are less commonly found in the colorectal region.  
  • Lymphomas: are the cancerous growths of the cells of the immune system. As with GISTs, lymphomas can occur anywhere along the digestive tract
  • Carcinoid tumors: these tumorous growths are in the hormone-producing cells of the gut associated with movement in gut and release of digestive juices. These tumors are mostly slow-growing. 
  • Turcot syndrome: this rare disorder occurs due to gene mutation and results in colon cancer, brain tumors, and colorectal polyp formation. 

What are the symptoms of colorectal cancer?

Commonly, patients with colorectal cancer complain of:

  • Change in the bowel habits with alternating constipation and diarrhea. 
  • Incomplete evacuation 
  • Bowel incontinence 
  • Unexplained anemia
  • Decreased appetite and weight loss
  • Weakness 
  • Bloating 
  • Vomiting 
  • Cramping in the gut 
  • Gnawing pain 
  • Rectal bleeding 
  • Dark, tarry stools
  • Upper GI bleed
  • Blood in vomitus 
  • Jaundice 

How is colorectal cancer diagnosed?

The diagnosis of colorectal cancer is based on thorough history and examination, followed by confirmatory investigations that also localize the tumor and determine its characteristics. These include:

  • Digital rectal examination
  • Complete blood count: there is unexplained anemia with colorectal cancers 
  • Tumor markers
  • Fecal occult blood test: is to test the stool for presence of blood cells, and is often positive in case of colorectal cancer.
  • Colonoscopy and sigmoidoscopy: a scope is inserted into the colon through the anus and the inside of the gut is examined for presence of polyps and obtaining a tissue sample. 
  • Imaging tests: investigations like CT, MRI and ultrasound of the gut are done to look for the size of tumors and spread of tumorous growths. 
  • biopsy

What are the treatment options?

According to experts like the Best Oncologist in Karachi treatment is based on surgical removal of the tumors, followed by chemo/radiotherapy.

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