The grade of a tumour refers to how abnormal the tumour cells look under a microscope. It is an indicator of how quickly a tumour is likely to grow and spread.
The more the cancer cells look like a normal cell, the more they will behave like a normal cell. Knowing the grade of a cancer helps the medical team to determine how effective a certain treatment may be.
- Grade 1: the cancer cells look similar to normal cells. These are referred to as “well differentiated cells”. Grade 1 tumours tend to grow and multiply slowly and are usually the least aggressive.
- Grade 2: the cancer cells look less like normal cells. These are referred to as “moderately differentiated cells”. These tumours tend to grow and spread faster than grade 1 tumours.
- Grade 3: the cancer cells have an abnormal appearance and do not look like normal cells. These are referred to as “poorly differentiated cells” or “undifferentiated cells”. These tumours tend to grow rapidly and spread faster than grade 1 and 2 tumours.