Pathogenia

author/s: Dr Dolores Maluenda Colomer


Why and where does colon cancer develop?

The microarchitecture of the colon is formed by crypts. These crypts have at their base – the deepest and furthest part from the intestinal lumen- progenitor cells, that is, immature cells that start to differentiate and finally, when they are already differentiated, they go up to the crypt surface and arrange themselves in contact with the intestinal lumen (superficial mature cells).

 

What is the role of superficial mature epithelial cells?

They protect the wall of the colon from the mutagenic environment inherent to the contents of the colon. The mucous contributes to this protection.

 

What is a gene?

Genes are like our cooking recipes needed to form our organs. A mutation in the gene means that our recipe has undergone a change in its writing and, in its turn, this alteration has caused the subsequent development of the tumour. It could be the equivalent to a cooking recipe where the sugar has been changed by salt: at the end, the meal tastes differently.

 

What is an oncogen?

An oncogen is a type of gene that if mutated results in the development of a cancer.

 

What other changes does the intestinal wall of the colon or rectum undergo?

Progenitor cells with mutated oncogenes give rise to uncontrolled cell proliferation that will constitute the tumour. This proliferation is replicated with an abnormal phenotype that makes it more susceptible to a second mutation. Thus, the presence of a single mutation in the APC gene creates all the necessary conditions to develop an adenoma: alteration in the proliferation, migration and cell adhesion.

 

Do all adenomas become malignant?

The neoplastic transformation of the adenoma requires being in contact with the colonic content.

 

How can we summarise the development of colon cancer?

In general, colon cancer derives from a well defined precursor lesion: an adenomatous polyp.

 Nearly all malignant tumours of the colon start as polyps.

The majority of these polyps are benign at the beginning, but occasionally a group of cells may appear with the ability to change into a cancer. Some experts consider that it takes about 10 years on average for a small adenomatous polyp (benign) to progress into a cancer. Approximately, 25% of these changes are caused by a genetic predisposition that is present from birth.

 

What is a polyp?

A polyp is a small wart-like tumour that appears in the intestinal lumen. Its correct definition is “a non invasive proliferation of epithelial cells”. It is said to be “non-invasive” because the mass in localised.

A polyp can adhere to the wall by means of a fine stem or pedicle –pediculated polyps- or by means of a wide implantation base –sesil polyps-.

 

Are there different types of polyps?

Yes.

Polyps are classified according to their morphology and histological characteristics. Tubular adenomatous polyps constitute 85%, tubular-vellous polyps a 10%, and vellous polyps a 5%.

 

Are there other types of polyps?

Yes. There are hyperplastic polyps, some of which can also degenerate.

 

Do all polyps have the ability to degenerate?

No. The likelihood for carcinomatous transformation is contingent upon the size, the proportion of vellous component and the age of the sufferer.

 

Can new polyps appear in a person?

Individuals whom diagnosed with polyps run a higher risk to that of the general population to develop new polyps. This risk varies depending on the size and the histological type (tubular, tubular-vellous and vellous).