Doctors use diagnostic tests like biopsies and imaging exams to determine a cancer's grade and its stage. While grading and staging help doctors and patients understand how serious a cancer is and form a treatment plan, they measure two different aspects of the disease.
What is a cancer grade?
A cancer’s grade describes how abnormal the cancer cells and tissue look under a microscope when compared to healthy cells. Cancer cells that look and organize most like healthy cells and tissue are low grade tumors. Doctors describe these cancers as being well differentiated. Lower grade cancers are typically less aggressive and have a better prognosis.
The more abnormal the cells look and organize themselves, the higher the cancer’s grade. Cancer cells with a high grades tend to be more aggressive. They are called poorly differentiated or undifferentiated.
Some cancers have their own system for grading tumors. Many others use a standard 1-4 grading scale.
- Grade 1: Tumor cells and tissue looks most like healthy cells and tissue. These are called well-differentiated tumors and are considered low grade.
- Grade 2: The cells and tissue are somewhat abnormal and are called moderately differentiated. These are intermediate grade tumors.
- Grade 3: Cancer cells and tissue look very abnormal. These cancers are considered poorly differentiated, since they no longer have an architectural structure or pattern. Grade 3 tumors are considered high grade.
- Grade 4: These undifferentiated cancers have the most abnormal looking cells. These are the highest grade and typically grow and spread faster than lower grade tumors.
What is a cancer stage?
While a grade describes the appearance of cancer cells and tissue, a cancer’s stage explains how large the primary tumor is and how far the cancer has spread in the patient’s body.
There are several different staging systems. Many of these have been created for specific kinds of cancers. Others can be used to describe several types of cancer.
Stage 0 to stage IV
One common system that many people are aware of puts cancer on a scale of 0 to IV.
- Stage 0 is for abnormal cells that haven’t spread and are not considered cancer, though they could become cancerous in the future. This stage is also called “in-situ.”
- Stage I through Stage III are for cancers that haven’t spread beyond the primary tumor site or have only spread to nearby tissue. The higher the stage number, the larger the tumor and the more it has spread.
- Stage IV cancer has spread to distant areas of the body.
Another common staging tool is the TNM system, which stands for Tumor, Node, Metastasis. When a patient’s cancer is staged with TNM, a number will follow each letter. This number signifies the extent of the disease in each category. According to the National Cancer Institute and MD Anderson experts, the standard TNM system uses the following rules:
Primary tumor (T)
- TX: Main tumor cannot be measured.
- T0: Main tumor cannot be found.
- T(is), or T in situ: The tumor is still within the confines of the normal glands and cannot metastasize.
- T1, T2, T3, T4: Refers to the size and/or extent of the main tumor. The higher the number after the T, the larger the tumor or the more it has grown into nearby tissues. T's may be further divided to provide more detail, such as T3a and T3b.
Regional lymph nodes (N)
Lymphatic fluid transports immune system cells throughout the body. Lymph nodes are small bean-shaped structures that help move this fluid. Cancer often first spreads to and through nearby lymph nodes.
- NX: Cancer in nearby lymph nodes cannot be measured.
- N0: There is no cancer in nearby lymph nodes.
- N1, N2, N3: Refers to the number and location of lymph nodes that contain cancer. The higher the number after the N, the more lymph nodes that contain cancer.
Distant metastasis (M)
Metastasis is the spread of cancer to other parts of the body.
- MX: Metastasis cannot be measured.
- M0: Cancer has not spread to other parts of the body.
- M1: Cancer has spread to other parts of the body.
We often hear about lymph nodes when we talk about how cancer spreads. That’s because when cancer starts to spread, it often goes to the lymph nodes first.
When treating breast cancer and melanoma, and – increasingly -- head and neck cancers and gynecologic cancers, physicians use a diagnostic method called sentinel lymph node biopsy, which looks at a patient’s lymph nodes to determine whether the cancer has spread and what type of cancer treatment is needed. At MD Anderson, our doctors often use sentinel lymph node biopsies because, in many cases, they help better detect cancer. In fact, about 20-30% of “node-negative” patients have disease present in their lymph nodes even though CT scans and/or ultrasound studies suggest that the lymph nodes are negative or do not contain disease.
We spoke with head and neck surgeon Stephen Lai, M.D., Ph.D., to learn more.
What is a sentinel lymph node biopsy?
Sentinel lymph nodes are an important part of the immune system, and they contain the cells that monitor foreign substances, like bacteria, viruses and cancer. Sentinel lymph node mapping helps to identify the lymph nodes that are at highest risk for containing cancer.
A sentinel lymph node biopsy (SLNB) is a surgical approach to identify and remove the sentinel lymph node to determine if the cancer has spread, and if so, how far.
In most cases, a negative sentinel lymph node biopsy means the cancer has not spread. A positive biopsy means cancer was found in the lymph node. It could be in other lymph nodes and even other organs.
What happens during a sentinel lymph node biopsy?
A surgeon injects a marker called a radiotracer around the site of the tumor. The radiotracer flows through the lymphatic system – a path or network of lymph channels and nodes. This allows the surgeon to see what lymph nodes are draining from the tumor first and identify a sentinel lymph node.
Then, the surgeon makes a small incision in the skin and identifies the lymph node for removal. A pathologist studies the lymph node to determine if it contains cancer.
What are the benefits of sentinel lymph node biopsy?
This technique uses a smaller incision and can prevent patients from needing a more invasive surgery. It can shorten postoperative recovery times and lower the risk of side effects like lymphedema, swelling caused by the removal of more lymph nodes.
A sentinel lymph node biopsy is often performed as an outpatient procedure, and patients are typically able to leave the hospital that day, unless they’re having additional surgery.
What are the risks of a sentinel lymph node biopsy?
The risks are very low risk, aside from the very low chance -- 2 to 4% -- that a sentinel lymph node would not be able to be identified.
Some patients have concerns about the radiotracer used to find the sentinel lymph node. While it is radioactive, the tracer has a very low-energy emission particle. No severe adverse reactions have been reported, and the only negative reaction reported has been rare episodes of brief pain during the injection.
Patients who have a sentinel lymph node biopsy may also experience lymphedema, but they’re less likely to than those who have an open surgery.
Tell me about advances in using sentinel lymph node biopsies to help more cancer patients.
Sentinel lymph node biopsy has been very well established for melanoma and breast cancer treatment. It’s also more commonly used in Europe for early-stage oral cavity cancer, and is being increasingly used in the U.S. I completed a Phase III clinical trial that led to the Food and Drug Administration approval of a new radiotracer for use in patients with oral cavity cancer. Now, I am leading an effort to start a Phase III clinical trial comparing sentinel lymph node biopsy to a more traditional technique called an elective neck dissection for early-stage oral cavity cancer patients. In addition, Michael Frumovitz, M.D., recently completed a Phase III clinical trial using a new type of dye in sentinel lymph node detection in patients with cervical and uterine cancers. These advances help us learn more about the cancer itself, while lessening side effects for patients.
Sentinel lymph node biopsy is personalized surgery. The surgery is tailored to the individual patient to target the lymph nodes most likely to harbor cancer. It helps patients get back to their everyday lives more quickly. It’s all about detecting the cancer effective and accurately in a way that helps the patients maintain their quality of life.
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