Overview

The stage of a cancer describes how much cancer is in the body and where it is located. If the cancer has spread, the stage also includes how far it has spread.

The grade describes how tumour cells look under a microscope compared to cells from healthy tissue near the tumour. The tumour grade may help predict how quickly the cancer will grow and spread.

Knowing the stage and grade of a cancer helps doctors know what treatment to use. It also helps predict how long the person will survive and what chance there is of a cure.

Cancer stages

There are several methods of cancer staging. Doctors may use this simple system to describe the overall stage of a cancer.

• Stage 0: Cancer hasn't spread.
• Stage I, II, or III: Cancer has grown or has spread into nearby tissues and perhaps lymph nodes. The higher the stage, the larger the tumour is or the farther the cancer has spread.
• Stage IV: Cancer has spread beyond the lymph nodes into other parts of the body (metastasized).

Doctors often need more details as they make decisions about treatment, so they may use the TNM method. The TNM method is based on:

• The size of the tumour (T).
• The spread of the cancer into nearby lymph nodes (N).
• The spread of the cancer to other body parts (M, for metastasis).

Most cancers can be described using the TNM system. But other staging systems are used for certain cancers (for example, cancers in children).

Tumour grades

A tumour's grade describes how its cells look under a microscope. Tumours are generally graded from 1 to 4. A lower number means more normal-looking cells and a lower likelihood that the cancer will spread quickly.

• A grade 1 tumour has tumour cells that look like normal cells. These tumours usually grow slowly.
• A grade 4 tumour has cells that look very different from normal cells. These tumours often grow quickly and spread rapidly.

Doctors use other grading methods for some types of cancer. For example, prostate cancers are graded with a Gleason score.