Cancers start from cells that were previously normal and healthy. These normal cells can usually be found surrounding a tumour. Pathologists use the word differentiated to describe the difference between the cancer cells and the surrounding normal, healthy cells.
Pathologists use the word differentiated in their report because not all cancers look the same. Some cancers look very similar to normal, healthy cells while others look very different.
Pathologists commonly use five levels to describe these changes:
Why is this important? In most parts of the body, well and moderately differentiated cancers tend to grow more slowly and are less likely to spread to other parts of the body. In contrast, poorly differentiated and undifferentiated cancers are aggressive tumours that grow quickly and spread earlier to other parts of the body.
Grade is another word pathologists use to describe the difference between cancer cells and the normal, healthy cells they have replaced. Grade is usually described using numbers to represent different levels. For example a tumour may be given a grade from 1 through 4. In this system, tumours that look similar to normal cells would be given a grade of 1 while those that look nothing like normal cells would be given a grade of 4. Grade can also be described using two levels, low and high.
For some types of cancer, the differentiation of the tumour is used to determine the grade. For example, each level of differentiation may equal a grade as shown below:
Or some levels of differentiation may be grouped together to make a grade:
Why is this important? Like differentiation, grade is used to help predict how the tumour will behave over time. Lower grade tumours tend to grow more slowly and are less likely to spread to other parts of the body. In contrast, higher grade tumours tend to grow faster and are more likely to spread to other parts of the body.
Talk to your doctor about how the tumour differentiation or grade described in your pathology report will be used to select the treatment options that are best for you.