What is pathology?

Dr Simon Nayler describes pathologists as the medical detectives trying to unravel the secrets of each tumour.


The treatment of any medical condition requires knowledge of what that illness is. Pathology is the study of disease and a histopathologist/pathologist is a medical specialist who diagnoses diseases based on the study of the tissues. 

They are responsible for examination of tumour tissue to make a definitive diagnosis and characterise each individual tumour.

A histopathologist’s training includes qualifying as a medical doctor, followed by an internship, and a further five-years specialising in tissue diagnosis.

Hidden member of MDT

The pathologist is an integral but often hidden member of the multi-disciplinary team (MDT). He/she provided insight into the unique disease processes at play in each patient. 

Although most people picture pathologists doing autopsies or forensic work, there are several different pathologists all contributing to overall patient management. 

Chemical pathologists deal with the chemistry of the body, particularly in body fluid. Haematologists deal with abnormalities of the blood and microbiologists deal with infectious diseases. Histopathologists diagnose disease processes based on tissue specimen and the changes therein. 

Responsibilities of pathologists

The histopathologist is responsible for the initial tissue diagnosis of cancer, and/or excluding benign conditions which may mimic cancers radiologically and clinically. 

All further management is reliant upon accurate tissue diagnosis. No cancer should ever be treated without histological assessment of the tumour.

Once the diagnosis has been made, the pathologist will then profile the tumour by determining the presence of biomarkers, which give an indication of the biological aggressiveness of the tumour. 

Some biomarkers may also predict the response to therapy and determine which chemotherapeutic agents could be used. 

The information pathologists provide in conjunction with other healthcare professionals will determine the next phase of the patient’s journey. 

Not seen but always present

Although the patient may never actually meet the pathologist in person, the pathologist is always present. Often in the wings (laboratory). 

Whether the patient has surgery primarily, or after chemotherapy or radiation therapy, the pathologist is often in attendance. They may well perform an intraoperative assessment (frozen section) of the resected specimen, such as the breast, to determine whether the surgeon needs to take extra margins and whether the lymph nodes are involved. This determines further surgical management. Often, this is the only time when the pathologist meets the patient.

After the surgical procedure, the pathologist determines the extent and stage of the tumour. He or she often performs further tests as this is the most representative specimen for definitively assessing tumour characteristics.

Personalising of the tumour

In 2019, the major function of the pathologist is a profiler of the tumour. To do this, they must utilise all the tools available, including the latest technology. 

In addition to evaluation of tissue sections (slides) of the tumour, the pathologist can evaluate the presence of biomarkers in the tissue utilising special stains. These include immunohistochemical stains and molecular tests to determine the presence of specific characteristics. This is called personalising of the tumour. Because each tumour is unique, this process is crucial in determining what future management may be required. 

The molecular testing will determine whether surgery, surgery with just radiation therapy, or chemotherapy would be most appropriate in each individual case. The pathologist is thus the medical detective trying to unravel the secrets of each tumour. 

When, despite all the best efforts of the team, tumours progress, the pathologist may still be able to detect new changes, or mutations which may allow for changes in treatment. Tumours are not necessarily static and may change their nature and characteristics. Some changes are amenable to newer and modified treatments.   

With increases in knowledge andrapid technological advancements,the battle against cancer is never over. The pathologist is at the vanguard of this battle, always up to date with the advancements trying to find a target to attack.

Dr Simon John Nayler (BSc, MBBCh, MMed, FFPath (SA)) is a director and consultant pathologist at Drs Gritzman and Thatcher Inc.

MEET OUR EXPERT – Dr Simon Nayler

Dr Simon John Nayler (BSc, MBBCh, MMed, FFPath (SA)) is a director and consultant pathologist at Drs Gritzman and Thatcher Inc.


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