When it comes to cancer, stages matter a lot, but most of us are unsure of what individual cancer stages mean and why they are so important. He’s an easy guide to cancer staging in order to help you better understand the confusing concept.

Cancer is a progressive disease, and stages help doctors better articulate how far the disease has spread and grown throughout the body. Staging also helps doctors understand what treatment option may work best to eliminate the cancer, Cancer.gov reports.

According to Cancer Research UK, cancer staging can also be used to describe the “grading” of the cancer, or how close the cancer cell is to a normal cell. For example, grade I cells look very similar to normal cells and do not grow rapidly, while grade III cells look abnormal and may grow or spread very aggressively. The following information has been compiled from Cancer.gov and Cancer Research Uk.

Stage 0

This usually means that a cancer is contained within the organ it started in. There is no evidence that it has broken off and begun to spread to other parts of the body, and treatment options usually involve surgically removing tumors.

Stage I

Stage I cancer is also small and usually has not spread to other organs. If it has spread, it is “localized” and has only gone to nearby tissue and not reached the lymph nodes or other body areas where is is far more dangerous.

Stage II

According to Cancer Research UK, this classification usually means the cancer has not started to spread into surrounding tissue but the tumor is larger than in stage 1. In addition, sometimes stage II means that cancer cells have spread into lymph nodes close to the tumor, depending on the particular type of cancer.

Stage III

Stage III cancer is usually larger, and may have started to spread into surrounding tissues and there are cancer cells in the lymph nodes in the area.

Stage IV

This category of cancer means the cancer has spread from where it started to another body organ, and is also called secondary or metastatic cancer.

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