Grading biliary tract cancers

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 cancer may be growing and how likely it is to spread.

Biliary tract cancers can start in the cells of either the gallbladder or bile duct. When cancer starts in gallbladder cells, it is called primary gallbladder cancer. When cancer starts in bile duct cells, it is called primary bile duct cancer. To find out the grade of a biliary tract cancer, a pathologist looks at a tissue sample from the gallbladder or bile duct 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.

The pathologist gives biliary tract cancers a grade from 1 to 3 (for gallbladder cancer) or 4 (for bile duct cancer). A lower number means the cancer is a lower grade.

Low-grade cancers have cancer cells that are well differentiated. This means that the cancer cells are abnormal but look a lot like normal cells and are arranged a lot like normal cells. Lower-grade cancers tend to grow slowly and are less likely to spread.

High-grade cancers have cancer cells that are poorly differentiated or undifferentiated. This means the cancer cells don't look 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.