July 25, 2023
In pathology, the term differentiated is used to describe the difference between cancer cells and normal, healthy cells. For example, a well differentiated tumour is made up of cells that look very similar to normal healthy cells. A moderately differentiated tumour is made up of cells that are clearly abnormal but still look similar normal cells. In contrast, a poorly differentiated or undifferentiated tumour is made up of cells that look very little like normal cells and additional tests such as immunohistochemistry may be needed to determine the cell type.
The difference between the cancer cells and the normal, healthy cells is important because better differentiated (well and moderately differentiated) tumours tend to grow more slowly and spread less frequently than less differentiated (poorly differentiated and undifferentiated) tumours.
The features used to determine the level of differentiation of a tumour depend on the cancer type 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 level of differentiation for most types of adenocarcinoma is based on the percentage of cancer cells making glands. In contrast, the level of differentiation in 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).