Cancer Staging and Grading
The TNM Classification System
- TX (presence of primary tumor cannot be assessed)
- T0 (no evidence of primary tumor)
- Tis (carcinoma in situ)
- T1 (small tumor)
- T2, T3 (medium-sized tumor)
- T4 (large tumor)
- NX (regional lymph nodes cannot be assessed)
- N0 (no regional lymph node involvement)
- N1, N2, N3 (increasing involvement of regional lymph nodes)
|Focus Box: Metastasis and the Lymphatic System|
|The lymphatic system is a network of channels that in many respects, resembles a sewer system. It drains excess fluid containing dead or damaged cells, other debris, toxins and bacteria from the tissues back into the blood vessels. The channels are periodically interrupted by clusters of lymph nodes found throughout the body, particularly in the neck, torso, axillae (armpits) and groin. As it passes through these lymph nodes, the lymph fluid is exposed to numerous specialized cells of the immune system (lymphocytes) that clear the fluid of the “trash”. Cancer cells leaving the site of a primary tumor quickly encounter a lymph channel, which carries them to the nearest lymph node cluster. For example, as breast cancer spreads, the cells are collected by the lymph channels in the breast and are taken to the axillary lymph node on the same side. This is why surgeons routinely remove many of these lymph nodes in that location to see if the cancer has already spread. Eventually, the cancer cells can reach the bloodstream where they may be transported to distant sites throughout the body.|
- MX (presence of distant metastasis cannot be assessed)
- M0 (no distant metastasis)
- M1 (distant metastasis present)
Putting T, N, M Together
|Image 1: Stage I and Stage II Breast Cancer|
|Image 2: Stage III and IV (Metastatic) Breast Cancer|
- GX (grade not assessable)
- G1 (well differentiated)
- G2 (moderately differentiated)
- G3 (poorly differentiated)
- G4 (undifferentiated); in other words, extremely poorly differentiated and bearing little resemblance to the tissue in which it arose)
|Focus Box: Cell Differentiation and Tumor Grading|
|Dedifferentiation is a process whereby cancer cells lose the distinctive cellular features that are characteristic of the tissues in which they arose. The better differentiated a cancer is, the more it resembles its tissue of origin and the more likely it is that the tumor will be less aggressive. The more poorly differentiated a cancer is, the less it resembles its tissue of origin, and the more likely it is to be aggressive. In poorly differentiated prostate cancer for example, doctors would find it difficult to identify the cancer cells as coming from the prostate gland if it were not for knowing the site in which the primary tumor is found and without relying on special stains that identify cellular markers found in prostate tissue. Additionally, poorly differentiated cells grow rapidly and without restraint, whereas well-differentiated cells (which closely resemble their tissue of origin) are either unable to proliferate or proliferate at a very slow rate. Aggressive cancers are often characterized by poorly differentiated cells, while less aggressive cancers tend to contain moderately or well differentiated cells.|
Cancer diagnosis. Merck Manual Professional version website. Available at: http://www.merckmanuals.com/professional/hematology-and-oncology/overview-of-cancer/cancer-diagnosis. Updated July 2013. Accessed May 12, 2015.
Cancer staging. American Cancer Society website. Available at: http://www.cancer.org/treatment/understandingyourdiagnosis/staging. Updated March 25, 2015. Accessed May 12, 2015.
Staging. National Cancer Institute website. Available at: http://www.cancer.gov/cancertopics/diagnosis-staging/staging. Updated March 9, 2015. Accessed May 12, 2015.
Tumor grade. National Cancer Institute website. Available at: http://www.cancer.gov/cancertopics/diagnosis-staging/prognosis/tumor-grade-fact-sheet. Updated May 3, 2013. Accessed May 12, 2015.
- Reviewer: Mohei Abouzied, MD, FACP
- Review Date: 03/2015 -
- Update Date: 05/12/2015 -
This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.
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