Understanding the Stages of Cancer

Updated: Nov 2


Cancer. It’s a small word that can mean a lot of different things. No matter what kind a person has, understanding the stages of cancer and available treatment options is important for optimal treatment.


A stage of a cancer mainly describes the size of the tumor and if it has spread to other areas of the body at the time of diagnosis. It is important for doctors to diagnose the stage of cancer so they can understand how serious the cancer is, as well as develop a prognosis.


Why staging is important


Identifying the stage of cancer acts as a guidepost for the surgical team and helps identify treatment plans or clinical trial options. If a cancer is localized to one area of the body, then surgery or radiotherapy could be enough to remove it completely. If a cancer has spread, chemotherapy, hormone therapy or biological therapies that circulate throughout the bloodstream are required.


How stages are determined


  1. X-rays

  2. Lab tests

  3. CT, MRI, PET or nuclear scans

  4. Ultrasounds

  5. Biopsy


There are different types of staging systems for different cancers, but the most common is the numbered cancer stage system, which identifies 5 possible stages:


  1. Stage 0 – Cancer cells that are still in the location where they started and have not spread.

  2. Stage 1 – Localized cancer that has spread into nearby tissues. It has not yet spread to lymph nodes or other areas.

  3. Stage 2 – Cancer has spread to a regional area or into nearby tissues or lymph nodes.

  4. Stage 3 – More advanced regional spread than Stage 2.

  5. Stage 4 – Cancer has spread to distant parts of the body. This stage is often referred to as metastatic cancer, or a cancer that has spread to other areas of the body.


This system gives doctors a common language to describe the size and spread of cancers. It is also helpful when comparing research studies and determining standardized treatment guidelines for hospitals and clinics.


Frequently Asked Questions Regarding Cancer Staging

What is cancer staging?

Cancer staging describes the extent of a cancer based on the cancer’s size and whether or not it has spread to other parts of the body. Staging helps doctors to determine the proper treatments and identify appropriate clinical trials.

When should cancer staging start?

The first step is diagnosing the cancer. It might be identified by screening tests like colonoscopies and Pap tests, or when the patient finds an abnormality, such as a breast lump, from a self-exam. Doctors perform various tests to stage a cancer, such as imaging studies like X-rays and CT scans or taking a biopsy. The test results enable the doctor to accurately stage the cancer and formulate the best treatment plan for the patient.

Why do we stage cancers?

Cancer staging can give doctors a sense of how aggressive the cancer is, which can help predict the cancer patient’s chances of survival. Staging also helps identify the best treatment approach to take. For example, a stage 1 colorectal cancer is usually treated differently from stage 3 or stage 4 colorectal cancer. Staging also identifies which patients can be included in clinical trials that are usually open only to people with stage 4 cancer.

What is the TNM staging system?

The TNM staging system describes the amount and spread of cancer in a patient’s body. It can describe cancer in great detail. Doctors use it to describe most types of cancer. Since the TNM system was developed by the American Joint Committee on Cancer, it’s also known as the AJCC staging system.

In the TNM system:


  • The T describes the size and extent of the main tumor and any spread of cancer into nearby tissue.

  • The N describes the spread of cancer to nearby lymph nodes.

  • The M describes metastasis, which is the spread of cancer to other parts of the body.

When a practitioner uses the TNM staging system to describe a cancer, they use numbers after each letter to give details about the cancer. For instance, an individual with stage 1 colorectal cancer may be assigned a grade of T1, N0, M0. This indicates that the tumor may have grown into a muscle layer in the gastrointestinal tract, but has not spread to lymph nodes or other parts of the body.

What is the difference between clinical staging and pathological staging?

Cancer staging can be “clinical” or “pathological.” Clinical staging means that it was done based on the results of tests performed prior to surgery, such as imaging scans and physical examinations. Pathological staging is based on what is discovered during surgery.

The clinical stage is typically indicated with a “c” before the TNM classification, and the pathological stage is indicated with a “p.” Pathological staging usually provides the most information for doctors in determining a patient’s prognosis.

Staging can also be done after an individual has received other treatments prior to surgery, such as chemotherapy, radiation therapy, or immunotherapy. This type of staging, known as the post-therapy stage, may be done for some cancers because treatment prior to surgery helps shrink the tumor so it can be removed. The post-therapy stage is indicated with a “y” before the TNM classification.

What cancers are not staged?

Not all cancers are staged, and some are staged differently than others. Most blood cancers, including leukemia, are not staged. This is because, at the time of diagnosis, the leukemia cells are already circulating throughout the body. Doctors describe leukemia as either active or in remission.

Brain tumors are also not staged. This is because, while they may spread to other parts of the nervous system, they rarely spread to lymph nodes. Instead, the tumor cells are graded from 1 to 4 to indicate how different they look from normal, healthy cells. Grade 4 cells are the most abnormal.

Small cell lung cancer is typically described as either limited stage or extensive disease. Limited stage means the cancer is limited to the chest. Extensive disease means it has extended outside the chest, which requires a different treatment approach.

Will restaging a cancer change the initial stage?

When a cancer is staged again after the first staging, it is referred to as restaging. Many times, the same tests that were performed when the cancer was initially diagnosed (such as imaging tests, physical exams, and biopsies) are done again. With restaging, the new stage classification is added to the original stage but doesn’t replace it. The stage assigned at diagnosis remains the most important one to record for statistics like survival rates.

What is a cancer grade, and how is it different from a cancer stage?

A cancer’s grade describes how abnormal the cancer cells look when compared to normal, healthy cells. Cancer cells that look most like normal cells are low-grade tumors. Lower-grade cancers are generally less aggressive and have more favorable prognoses.

The more abnormal the appearance of the cells, the higher the cancer’s grade. Cancer cells with high grades tend to be more aggressive. Doctors refer to them as poorly differentiated or undifferentiated.

Many types of cancers, but not all, use a standard 1 to 4 grading scale:

  • Grade 1: These tumor cells look most like healthy cells. They are called well-differentiated tumors and considered low-grade.

  • Grade 2: The cells are somewhat abnormal and are referred to as moderately differentiated. These are intermediate-grade tumors.

  • Grade 3: These look very abnormal. They are considered poorly differentiated since they no longer have an architectural structure or pattern. Grade 3 tumors are considered high grade.

  • Grade 4: These have the most abnormal-looking cells. They are the highest grade and typically spread faster than lower-grade tumors.

While a grade describes the appearance of cancer cells and tissue, a cancer’s stage explains the size of the primary tumor and how far the cancer has spread in the body.

What are primary and secondary tumors?

In medical terminology, “primary” refers to the original site of the tumor. “Secondary” refers to any other sites where the cancer has spread. It is not uncommon to identify secondary tumors from a cancer without being able to identify the “primary,” or original, source. The medical term for this is “carcinoma of unknown primary.”


If you’ve been recently diagnosed with cancer or would like to learn more about treatment options, call the START Center today at (210) 593-5700 or request an appointment.


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