Grading anal cancer

Grading describes how the cancer cells look compared to normal, healthy cells. Knowing the grade gives your healthcare team an idea of how quickly the anal cancer may be growing and how likely it is to spread. The grade is also used to describe precancerous conditions of the anus.

To find out the grade of anal cancer, a pathologist looks at a tissue sample from the anus under a microscope. They look at how different the cells look from normal cells (called differentiation) and other features of the tumour such as the size and shape of the cells and how the cells are arranged. They can usually tell how fast a tumour is growing by looking at how many cells are dividing.

Low-grade cancers have cancer cells that are well differentiated or moderately differentiated. The cells are abnormal but look a lot like normal cells and are arranged a lot like normal cells. Lower-grade cancer cells tend to grow slowly and are less likely to spread. Moderately differentiated anal cancer grows slightly faster than well differentiated anal cancer.

High-grade cancers have cancer cells that are poorly differentiated or undifferentiated. The cells don't look or act like normal cells and are arranged very differently. Higher-grade cancers tend to grow more quickly and are more likely to spread than low-grade cancers. Undifferentiated anal cancer grows faster and spreads more quickly than poorly differentiated cancer.