Prognosis of cancer varies according to the stage of the cancer. Staging and grading of cancer helps determine the course of the treatment. Go through this article to know the terms that are used to describe the stage and grade of a cancer.
Cancer is a life-threatening disease which does not occur suddenly. It develops slowly and in most cases, exhibits symptoms in its advanced stages. Detection of cancer in its early stages helps remove the cancer completely from the body. Advanced technology and therapies like chemotherapy and radiation therapy help kill the remaining cancer cells and thus help minimize the chances of its recurrence. The analysis of cancerous cells based on the site of origin and lab reports, is termed as ‘grading of cancer’ while determining the extent of cancer (whether cancer has spread to locations other than its origin, and if yes, how much or to how many places) is referred to as ‘staging of cancer’.
Doctors first examine the symptoms of the disease. Certain tests like CT scan, X-rays, ultrasound and a biopsy help diagnose cancer. With the help of the test reports, the doctor estimates how big the tumor is or what is the stage of cancer (whether it has invaded nearby lymph nodes, organs and distant organs). This is called clinical staging of cancer. Generally, a surgery is performed (if possible) to remove the cancer. In a laboratory, the removed tissue and lymph nodes are microscopically examined. The pathologist presents a report on staging and grading of cancer after actual observation of the cancerous cells. This is known as pathological staging. It gives an exact idea about the origin, nature and spread of cancer.
According to its origin, cancers are classified as follows:
- Myeloma- cancer originated in the bone marrow
- Sarcoma-originated in the connective or supportive tissue (e.g., bone, cartilage, muscle)
- Carcinoma-origin in the epithelial tissue (i.e., tissue that lines organs and tubes)
- Adenocarcinoma-originated in the glandular tissues
- Blastoma-originated in the embryonic tissue of organs
- Lymphoma-origin in the lymphatic tissue
- Leukemia-cancer initially developed in the tissues that form blood cells
For solid tumors, TNM (Tumor, Node, Metastasis) system is used for grading of cancer. It is not used to describe brain tumors and hematological malignancies. In the U.S., Jewett-Whitmore system is sometimes used to describe prostate cancer. Staging and grading of prostate cancer is done with the help of TNM system in the rest of the world. Grades are denoted by numbers 1 to 4. The abnormality of cells determine the grade of cancer. Higher grade indicates higher abnormality of the cells.
- Grade 1: Cells are slightly abnormal and are well differentiated.
- Grade 2: Cells are more abnormal and are moderately differentiated.
- Grade 3: Cells are highly abnormal and are poorly differentiated.
- Grade 4: Cells immature and undifferentiated.
The roman numeral staging helps understand the spread of cancer. Staging helps understand the growth pattern or progression of cancer and hence helps determine the correct treatment. It also plays an important role in the life expectancy of the patient or the survival rate. Survival rate is low for higher stages.
- Stage 0: This stage is also called ‘carcinoma in situ’. For example, some abnormal cells which are likely to turn cancerous are detected in the Pap smear test. Pap smear test has helped increase the survival rate of cervical cancer in women significantly, over the last few decades.
- Stage I: Cancer is confined to one part (its origin) of the body.
- Stage II: Cancer spreads locally.
- Stage III: Extensive local and/or regional spread of cancer. The specific criteria for Stages II and III may vary according to the type of cancer. Cancer affecting the lymph nodes, cancer invading lymph nodes on only one side, or invading the lymph nodes on both sides, etc. are reported as stage II and stage III, depending upon the type of cancer.
- Stage IV: Metastasized cancer. Cancer has spread into other distant organ(s) or throughout the body.
The letters ‘c’ and ‘p’ indicate whether the report refers to clinical or pathological staging (e.g., cT2N1M0 or pT1N0).
- T0 indicates no evidence of tumor
- Tis stands for carcinoma in situ (abnormality limited to surface cells)
- T1 to 4 indicates smaller/larger size of the tumor and whether it has gone deep into the skin or surrounding tissue.
- N0 indicates nearby lymph nodes are not invaded by cancer.
- N1 to 4 stand for degree of lymph node invasion (how many lymph nodes are invaded).
- TX and NX indicate tumors cannot be assessed or lymph node invasion cannot be assessed.
- M0 shows no evidence of distant metastases.
- M1 indicates distant metastases.
Researchers are busy in developing new, highly sensitive methods of staging and grading of cancer as treatment, diagnosis and staging are all interrelated.