What Do Stage Letters Like 2A and 3B Mean?

This page is for people who see a stage with a letter on it, such as 2A, IIB or 3C. It explains what the letter adds and shows how it works in three cancers.

Stage tells you how large a cancer is and whether it has spread. NCI's chart lists stage 0, stages I to III, and stage IV. In general, a higher number means a more advanced cancer. Stage IV means the cancer has spread to distant parts of the body.

NCI also says that letters and numbers are often added after the first number to describe the cancer in more detail. Its example is prostate cancer. Stage 2 may be divided into 2A, 2B or 2C.

NCI says there are many staging systems. Some are used for many cancers, like the TNM system. Others are made for one type of cancer. Blood cancers and brain and spinal cord tumors, for example, have their own systems.

That is why you cannot compare letters between cancers. The examples below come from NCI's cancer summaries for health care teams and patients.

In colon cancer, stage II is divided by how far the cancer has grown through the wall of the colon.

• Stage IIA: the cancer has spread through the muscle layer of the colon wall to the outermost layer, called the serosa.
• Stage IIB: the cancer has spread through the serosa to the tissue that lines the organs in the belly.
• Stage IIC: the cancer has spread through the serosa to nearby organs.

In stage III colon cancer, the letters A, B and C depend on two things. One is how deep the cancer has grown. The other is how many nearby lymph nodes have cancer.

In ovarian cancer, stage I is divided into IA, IB and IC.

• Stage IA: cancer is found inside a single ovary or fallopian tube.
• Stage IB: cancer is found inside both ovaries or fallopian tubes.
• Stage IC: cancer is found inside one or both, and one of a few other things is also true. For example, the tumor or the ovary's outer covering has broken open.

Stage III is divided into IIIA, IIIB and IIIC. IIIB means cancer has spread to the peritoneum outside the pelvis, such as the omentum, and that cancer is 2 centimeters or smaller. IIIC means that cancer is larger than 2 centimeters. The peritoneum is the tissue that lines the belly, and the omentum is a fold of it that surrounds the stomach and other organs.

For prostate cancer, NCI says the stage is based on the PSA level and the Grade Group, along with how much of the prostate has cancer and whether it has spread. PSA is a protein made by the prostate that is measured in a blood test.

So the letters here follow test results, not only size. NCI describes stage IIB as Grade Group 2. It describes stage IIC as Grade Group 3 or 4.

Letters and numbers also appear inside the TNM system. NCI says T and its number describe the size and spread of the main tumor, and that a T may be divided further, such as T3a and T3b. You can read more on the pages about TNM staging and T stage.

NCI says a cancer is always referred to by the stage it was given at diagnosis, even if it gets worse or spreads. So your stage letter does not change as time passes. New information is added to the original stage.

Your stage letter is not an emergency by itself. Ask your care team when the rest of your results will be ready and when treatment planning starts. If you have new or worsening symptoms while you wait, call your care team right away. If you think you are having an emergency, call 911.

• What is my full stage, including the letter?
• What does that letter stand for in my type of cancer?
• Which results were used to set my stage?
• How does my stage affect my treatment options?

• National Cancer Institute: Cancer Staging
• National Cancer Institute: Colon Cancer Treatment (PDQ), Patient Version
• National Cancer Institute: Ovarian, Fallopian Tube, and Primary Peritoneal Cancer Treatment (PDQ), Patient Version
• National Cancer Institute: Prostate Cancer Treatment (PDQ), Patient Version