The term “grade” of a cancer is often confused with the term “stage”. The two are completely different. This article discusses the meaning of “grade” of a cancer and its importance for someone dealing with cancer.
In early 2017, when I moved to the hospital I currently work in, one of the first patients I saw was 65-year-old Mrs Janaki (name changed). She was referred to me after a colonoscopy showed a growth in her sigmoid colon, and the biopsy confirmed the presence of a cancer. At our first meeting, she and her husband were in tears – “I saw the biopsy report. It says I have grade 4 cancer. That means its terminal, isn’t it?” It took me a while to explain to her that she was confusing grade 4 with stage 4. Finally it turned out she had stage 2 cancer – she underwent a laparoscopic resection of her sigmoid colon, required no further treatment at all, and is living a healthy and active life today.
The grade of a cancer indicates how much the cells of a particular patient’s cancer resemble the normal cell of origin. This is determined by the pathologist who studies the biopsy sample of the patient’s cancer under the microscope.
Grade 1: cancer cells looks almost like normal cells
Grade 2: cancer cells looks less normal
Grade 3: cancer cells look quite different from normal cells
Grade 4: cancer cells don’t resemble normal cells at all
On the other hand, “stage” of a cancer is the extent of spread of the cancer. A stage 1 cancer is still small and confined to the organ of origin, whereas a stage 4 cancer is one which has spread to different places in the body. Thus, grade and stage are distinct entities. Someone could have a stage 1 grade 4 cancer, and someone else a stage 4 grade 1 cancer.
Grade of a cancer can be expressed in different ways in a pathology report. The grade could be numbered as described above – for example a report could say “grade 2 breast cancer”. Some reports could just mention low grade (includes grade 1 and 2) or high grade (includes grade 3 and 4). Other terms used by pathologists are well differentiated (for grade 1), moderately differentiated (for grade 2), poorly differentiated (for grade 3) and undifferentiated (for grade 4).
Cancer grade is important in oncology practice for several reasons:
1. Prognosis: In general, the higher the grade, the more aggressive the cancer. In cancer, prognosis refers to the chance of cancer progression or cancer recurrence. But the importance of grade in determining prognosis depends on the type of cancer. For some cancers (like prostate cancer) grade has a major impact on prognosis. For other cancers, it may be only a minor prognostic factor. Also, grade is just one of the many different factors which influence prognosis. The importance of grade for an individual patient with cancer can only be determined after taking all prognostic factors into consideration.
2. Primary treatment: For many cancers the grade may not influence the treatment required. But for other cancers, the grade may be a key factor that determines the extent of treatment (eg. whether to sample the lymph nodes or not during surgery for a uterine cancer).
3. Additional treatment: For some cancers, the grade is an important factor that determines the need for adjuvant treatment. For example a low-grade soft tissue sarcoma may not require any treatment following surgery, whereas a high-grade sarcoma may require adjuvant radiotherapy.
To summarize, cancer grade is a distinct entity not to be confused with cancer stage. The implications of grade for prognosis as well as treatment is different for different cancers.