When planning treatment for rectal cancer, the cancer's grade and stage are of critical importance. Rectal cancer grading refers to how different cancer cells appear under a microscope compared to normal cells. This grading provides crucial information about the cancer's growth rate and its potential for metastasis (spread).

In low-grade rectal cancer, although the cells are abnormal, they show a structure that is more similar to normal cells. These types of cancers generally grow slower and have a lower risk of metastasis.

In high-grade rectal cancer, however, the cells are significantly differentiated from normal cells, having a more anaplastic structure. High-grade cancers generally tend to grow faster and have a higher likelihood of spreading to other parts of the body (metastasizing) compared to low-grade ones.