by Jason Wasserman MD PhD FRCPC
June 1, 2022
Differentiated is a term pathologists use to describe the difference between cancer cells and normal, healthy cells. Most types of cancer are divided into three grades of differentiation – well differentiated, moderately differentiated, and poorly differentiated. For some types of tumours, a fourth grade called undifferentiated is also used. The grade is important because more differentiated cancers (well and moderately differentiated) tend to grow more slowly and spread less frequently than less differentiated cancers (poorly differentiated and undifferentiated).
The features used to determine the grade of differentiation depends on the type of cancer and the normal cells being used for comparison. For example, most types of adenocarcinoma start from cells that normally make round structures called glands. For this reason, the grade of differentiation for most types of adenocarcinoma is based on the percentage of cancer cells making glands. In contrast, the grade of differentiation in a squamous cell carcinoma is based on how much the cancer cells look like the normal squamous cells found on the surface of a tissue (such as the skin).