Grade 3 cancer is characterized by the presence of poorly differentiated tumor cells and tissue, notes the United States' National Cancer Institute. In terms of appearance, growth rate and growth patterns, the extent in which these cells and tissue varies to normal cells, is high.
Cancer grade is a numerical rating that refers to the observable degree of abnormality of malignant cells and tissue under a microscope. Different types of cancers have their own corresponding grading systems. As a general rule, a scale of 1 to 4 is used if the specific grading system is unknown. A "GX" rating is given to a tumor type with an "undetermined grade."
Grade 3 cancer is considered to be a high-grade cancer grade classification. Unlike Grade 1 cancer cells that tend to grow and spread at a slower rate, Grade 3 tumor cells and tissue proliferate at a much faster rate. These cells also multiply in disorganized and random patterns, such as those found in Grade 3 breast cancer. Compared to low-grade cancer cells that are well-differentiated and only have slight variations with normal cells, high-grade malignant cells do not develop normal structures when they specialize into tissues.
A low-grade cancer typically has a better prognosis than a high-grade malignancy. However, higher-grade tumors, such as Grade 3 cancer, may prove more susceptible to common cancer treatments, including chemotherapy and radiation therapy, notes Breastcancer.org.