[Original article on NHS Choices website]

The stage of a cancer describes the size of a tumour and how far it has spread from where it originated. The grade describes the appearance of the cancerous cells.

If you’re diagnosed with cancer, you may have more tests to help determine how far it has progressed. Staging and grading the cancer will allow the doctors to determine its size, whether it has spread and the best treatment options.

Cancer stages

Different types of staging systems are used for different types of cancer. Below is an example of one common method of staging:

stage 0 – indicates that the cancer is where it started (in situ) and hasn’t spread

stage I – the cancer is small and hasn’t spread anywhere else

stage II – the cancer has grown, but hasn’t spread

stage III – the cancer is larger and may have spread to the surrounding tissues and/or the lymph nodes (part of the lymphatic system)

stage IV – the cancer has spread from where it started to at least one other body organ; also known as “secondary” or “metastatic” cancer

Cancer grades

The grade of a cancer depends on what the cells look like under a microscope.

In general, a lower grade indicates a slower-growing cancer and a higher grade indicates a faster-growing one. The grading system that’s usually used is as follows:

grade I – cancer cells that resemble normal cells and aren’t growing rapidly

grade II – cancer cells that don’t look like normal cells and are growing faster than normal cells

grade III – cancer cells that look abnormal and may grow or spread more aggressively