Once you receive a cancer diagnosis, your medical team will strive to understand everything about your cancer: where the cancer cells are in your body, how fast they’re spreading and how abnormal they’ve become. As cancerous cells grow, they may form tumors (clumps of cells) and travel throughout the body.
All of these factors are used to establish a treatment plan, and for this reason, doctors will assign a stage number to your cancer and a grade to your tumor as applicable.
“These numbers are a good starting point and an important thing to know, but there is a lot of nuance to what stage and grade mean for you, and it differs by cancer,” says Hung-Jui (Ray) Tan, MD, a UNC Health urologic oncologist. “It’s best to talk to your clinical team to understand your specific diagnosis.”
Although there are several systems for staging cancers and grading tumors, here is a basic overview of how the categories are determined and why they are important to your medical team.
Cancer Stages
The stage of cancer refers to how much the disease has spread in your body. Different cancers may use different staging systems. One common system is TNM, which assigns a number to the size, location and growth of the tumor (T); whether it has spread to the lymph nodes (N); and how far the cancer has spread from its original location, or metastasized (M).
Doctors will use this system to assign a stage number, typically 1 to 4. A lower number means less spread, and a higher number means more spread.
Some cancers use different staging systems, and some cancers aren’t staged at all.
Notably, brain cancer is not typically staged because those tumors rarely spread beyond the brain.
Also, blood cancers have unique staging systems or none at all. Stages of lymphoma, a type of blood cancer in which masses form in the lymph nodes, depend on the number of affected lymph nodes and the location of the masses.
“A stage 4 lymphoma is very different from a stage 4 solid organ cancer,” says Christopher Dittus, DO, a UNC Health hematologist and oncologist. “The stage is one factor of many.”
Many people fear hearing the words “stage 4” in relation to cancer, thinking that it’s an incurable disease. Although stage 4 cancers are advanced and may require aggressive treatment, it is not necessarily terminal or an indication of how long you’ll live.
Tumor Grades
The grade of a tumor represents how abnormal its cells are. If you’ve had a biopsy (sample taken) or a resection (surgical removal) of a tumor, that tissue will be sent to a laboratory for testing and analysis. Using a microscope, a doctor called a pathologist will evaluate the cells that make up the tumor.
“We compare the appearance of that tissue’s normal cells with the cancerous cells,” says UNC pathologist Sara Wobker, MD, MPH. “We’re looking at whether the cell from the tumor is more or less like the original cell.”
If a tumor cell still resembles a normal cell, it’s considered well-differentiated. Abnormal cells with significant changes from the normal cells are considered poorly differentiated or undifferentiated.
Pathologists will assign the tumor a grade number on the spectrum of differentiation, with 1 being a well-differentiated or low-grade tumor and 4 being an undifferentiated or high-grade tumor. High-grade tumors generally grow and spread more quickly.
As with staging, grading criteria may vary for different types of tumors.
In addition to grading the tumor, the pathologist identifies other information that could affect your treatment.
“We’re looking for potential biomarkers that could predict how you’ll respond to immunotherapy,” Dr. Wobker says, referring to a treatment method that uses the body’s own immune system to fight cancer. “We can sometimes identify markers of how fast a tumor will grow.”
Why Stages and Grades Matter
Cancer stage and tumor grade are just two factors—albeit important ones—that will affect the route of your cancer journey, Drs. Tan, Dittus and Wobker emphasize. Other factors include your health and the potential side effects of treatment.
“Your physician and clinical team can recommend treatments that are appropriate, because low-grade, low-stage treatment is different from high-grade, high-stage treatment,” Dr. Tan says. “Keep in mind that it differs by cancer. I see men with stage 1 or 2 prostate cancer where observation and surveillance may be all they need. An advanced stage could mean something really serious, or it could mean that the person has many years ahead of them with good treatment.”
Staging can also determine your eligibility for clinical trials, in which volunteers receive emerging treatments that are studied for their effectiveness. To evaluate how well a new treatment or intervention is working, researchers will form groups of people with a similar stage of cancer.
If you have questions about your cancer diagnosis or treatment plan, talk to your doctor. Don’t have a doctor? Find one near you.