Colon cancer as diagnosed by a pathologist
Colon cancer as diagnosed by a pathologist

A pathologist is a doctor who has specialised in the causes and diagnosis of disease.

In Australasia, this involves at least five years of postgraduate training after qualifying as a doctor.

“Many people think of pathologists as those rather eccentric individuals performing autopsies in television shows like Silent Witness,” Associate Professor Chris Hemmings from St John of God Pathology.

“But actually far more pathologists spend their time diagnosing cancer and other diseases, by examining tissue microscopically.”

In bowel cancer cases, by knowing what the normal bowel lining (mucosa) looks like, it is possible to see changes in structure that indicate that a polyp or a cancer has developed.

“We can see various types of polyps, and some of these will not turn into cancer, but one common type of polyp called an adenoma is known to progress to cancer in some cases, if it is not removed,” A/Prof Hemmings says.

“Complete removal of the adenoma before the cancer develops will prevent cancer from arising in that adenoma, but we know that people who develop one adenoma are more likely to develop further ones in future.”

“So these people need to be followed up to remove new adenomas in subsequent years.”

Cancer is diagnosed when the growth has spread beyond the mucosa into the deeper layers of the bowel wall.

In most cases, the patient will then require surgery to remove the affected portion of the bowel where the cancer developed.

“The pathologist will then examine the segment of bowel to ascertain how far the cancer has spread, whether it has been completely removed, and whether there are additional risk factors (such as cancer growing into blood vessels) which mean it is more likely to come back,” A/Prof Hemmings says.

“If the cancer is advanced, chemotherapy treatment may be recommended, and in this case the pathologist may also test the cancer tissue for various mutations which may help guide the selection of the most appropriate drugs for that patient.”

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