June 26, 2023

What does atypical mean?

In pathology, the term atypical is used to describe cells that look abnormal either in shape, colour, or size compared to normal, healthy cells in the same location. Pathologists may also describe these changes as cytologic atypia.

atypical cell
Atypical cell
What causes a cell to become atypical?

There are many reasons why cells may start to look atypical. The most common causes include:

  • Inflammation – Inflammation is the body’s natural defense against injury or disease.  The body also uses inflammation to repair tissue after an injury has taken place. The special cells that take part in inflammation are called inflammatory cells and they are part of the body’s immune system. Normal, healthy cells can start to look atypical when they are close to inflammatory cells. In this situation, the atypia goes away when the inflammation stops.
  • Infection – Cells that become infected by a virus can look very atypical. Pathologists sometimes call this type of atypia viral cytopathic effects. The atypical cells will go away once the infection is removed from the body.
  • Radiation – Radiation is a common treatment for cancer. Normal, healthy cells that have been exposed to radiation commonly look very atypical when examined under the microscope. Your doctor should always let your pathologist know if you are receiving currently radiation or have received radiation in the past.
  • Pre-cancerous diseases – The abnormal cells in most pre-cancerous diseases look atypical when examined under the microscope. Pre-cancerous diseases that show atypical cells include dysplasia and carcinoma in situ.
  • Cancer – Almost all cancers are made up of cells that look atypical compared to the normal, healthy cells around them. In this case, atypia is very important because it helps your pathologist make the diagnosis and determine the tumour grade.

It is important to remember that atypical is a description of the way some cells look and not a complete diagnosis by itself. In many cases, your pathologist will try to determine the cause of the atypical cells. If the cause is known, it will be described in your pathology report. However, your doctors may only be able to determine the cause of the atypical cells later with the help of additional information about you and your medical history.

Does atypical mean cancer?

No. Atypical does not mean cancer. Atypical is a term pathologists use to describe cells that look abnormal when examined under a microscope. Atypical cells can be seen in cancerous tumours and a variety of non-cancerous conditions such as an infection, inflammation, or after radiation treatment.

Can atypical cells be benign?

Yes. Atypical cells can be benign (non-cancerous). Cells in an area of inflammation or prior radiation can look atypical but are still benign.

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