A Beginner’s Guide to Understanding Cancer Stages & Grades

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Medically Reviewed By:
Mark Arredondo, M.D.

One of the first questions many newly diagnosed cancer patients have is how advanced their disease is.

With 1.9 million new cancer cases diagnosed each year in the United States, understanding cancer stages and grades can better inform your treatment decisions.

Whether you or a loved one faces this alarming diagnosis, this beginner's guide is designed to help you better understand how many stages of cancer there are and what they mean, so that you can make more informed decisions and find clarity during a challenging time.

Stages of cancer

Cancer staging is a critical component in determining the extent and severity of the disease, helping health care professionals chart an effective treatment plan. Most cancers, including solid tumors, adhere to the TNM (Tumor, Node, Metastasis) system, which evaluates the size and location of the tumor, lymph node involvement and whether the cancer has spread to distant organs.

Cancer staging and grading offer essential information to cancer care teams while formulating a patient's treatment strategy. Dr. Ajaz Khan, enterprise chair of medical oncology at City of Hope Chicago, pointed out in a recent article that staging can influence a patient's prognosis. Generally, cancers detected in stages 0 to 2 often lead to more favorable long-term outcomes than those diagnosed in stages 3 or 4.

However, it's important to note that not all cancers follow this staging pattern, such as blood cancers like leukemia or multiple myeloma. The Cleveland Clinic provides a simplified breakdown of the four primary cancer stages. While these four stages are the most common, there’s also a Stage 0. This stage is usually easily treatable and is considered precancerous by most experts.

  • Stage I: In this phase, cancer is limited to a small area and hasn't spread to adjacent lymph nodes or other tissues. Early detection and intervention can lead to favorable outcomes.

  • Stage II: Cancer has progressed, but it is still localized and has not spread beyond its initial site. While it's more advanced than Stage I, it remains treatable with various therapeutic approaches.

  • Stage III: The cancer has grown further and might have invaded nearby lymph nodes or surrounding tissues. Treatment plans may involve a combination of surgery, radiation and chemotherapy.

  • Stage IV: Also known as metastatic or advanced cancer, Stage IV signifies that cancer has spread to distant organs or regions of the body. It is often the most challenging stage to treat, requiring advanced therapies tailored to each patient's unique circumstances.

Stages for leukemia

Leukemia, a form of blood cancer, and the 10th most common form of cancer, according to the Cleveland Clinic, develops in the blood and bone marrow. It differs from solid tumors in its nature and staging process. This cancer arises from the excessive production of abnormal white blood cells, impairing the immune system's ability to combat infections and affecting red blood cell and platelet production.

Staging leukemia follows a unique system, often using the Rai system for chronic leukemia, as described by the Moffitt Cancer Center:

  • Stage 0: Patients have elevated white blood cell counts but no other symptoms.

  • Stage 1: Patients display increased white blood cell counts and enlarged lymph nodes.

  • Stage 2: In this phase, patients have elevated white blood cell counts, may be anemic and often present with enlarged lymph nodes.

  • Stage 3: Similar to Stage 2, patients have high white blood cell counts, anemia and may also have enlarged lymph nodes or an enlarged liver or spleen.

  • Stage 4: At this advanced stage, patients have high white blood cell counts, low platelet levels, anemia, enlarged lymph nodes and an enlarged liver or spleen.

Cancer grades

The MD Anderson Cancer Center explains that cancer's grade refers to the degree of abnormality observed in cancer cells and tissues under a microscope compared to their healthy counterparts.

Tumors with cancer cells closely resembling normal tissue are classified as low-grade, often termed "well-differentiated" by physicians. These lower-grade cancers are less aggressive and offer a more favorable prognosis.

Conversely, the cancer's grade rises as cells become increasingly abnormal in appearance and organization. Cancer cells with high grades are generally more aggressive and are referred to as "poorly differentiated" or "undifferentiated."

While some cancer centers employ unique grading systems, many adopt a standard scale:

  • Grade 1: Tumor cells and tissue closely resemble healthy counterparts, termed "well-differentiated" and considered low grade.

  • Grade 2: Cells and tissue display moderate abnormalities, referred to as "moderately differentiated," marking intermediate-grade tumors.

  • Grade 3: Cancer cells and tissue exhibit pronounced abnormalities, losing their architectural structure or pattern, categorizing them as "poorly differentiated" and signifying high grades.

  • Grade 4: These cancers, known as undifferentiated, showcase the most extreme abnormalities in cell appearance. They represent the highest grade and typically grow and spread faster than lower-grade tumors.

Providing critical guidance for cancer care teams

Cancer care is advancing, with cancer mortality rates progressively declining over the years. From the late 1990s to 2019, the pace of decline in cancer mortality has accelerated, largely driven by advancements in lung cancer detection and treatment.

Understanding cancer stages and grades is vital in this progress, guiding treatment decisions and providing hope for improved outcomes in the fight against cancer.


American Cancer Society: Cancer Facts & Figures 2022

Cleveland Clinic: Cancer

Cleveland Clinic: Leukemia

Moffitt Cancer Center: Staging Leukemia

American Society of Hematology: Blood Cancers

MD Anderson Cancer Center: Cancer Grade vs. Cancer Stage

American Cancer Society Journals: Cancer Statistics, 2022

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