Staging is a way of describing where the cancer is located, if or where it has spread, and whether it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the cancer’s stage, so staging may not be complete until all of the tests are finished. Knowing the stage and histologic grade of cancer helps the doctor to decide what kind of treatment is to be given and can help predict a patient’s prognosis (chance of recovery). There are different stage descriptions for different types of cancer.
One tool that doctors use to describe the stage is the TNM system. This system judges three factors: the tumor itself, the lymph nodes around the tumor, and if the tumor has spread to other parts of the body. The results are combined to determine the stage of cancer for each person. There are five stages: stage 0 (zero) and stages I through IV (one through four). The stage provides a common way of describing the cancer so doctors can work together to plan the best treatments.
TNM is an abbreviation for tumor (T), node (N), and metastasis (M). Doctors look at these three factors to determine the stage of cancer:
- How large is the primary tumor, and where is it located? (Tumor, T)
- Has the tumor spread to the lymph nodes? (Node, N)
- Has the cancer metastasized (spread) to other parts of the body? (Metastasis, M)
Tumor. Using the TNM system, the "T" plus a letter or number (0 to 4) is used to describe the size and location of the tumor in NPC. Some stages are also divided into smaller groups that help describe the tumor in even more detail. Specific tumor stage information is listed below.
TX: The primary tumor cannot be evaluated.
T0: No evidence of a tumor is found.
Tis: This describes a stage called carcinoma (cancer) in situ. This is a very early cancer where cancer cells are found only in one layer of tissue.
T1: The tumor has not spread beyond the nasopharynx.
T2: The tumor extends into the soft tissue of the middle throat.
T3: The tumor extends into bony structure or into the area behind the nose.
T4: This describes a tumor that extends inside the head to the area of the brain or into the lower part of the throat.
Node. The “N” in the TNM staging system is for lymph nodes, the tiny, bean-shaped organs that help fight infection. Lymph nodes near where the cancer started are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes.
In people with NPC, doctors examine lymph nodes in a triangle-shaped area formed by three points: where the neck meets the shoulder, where the collarbone joins the tip of the shoulder, and where the front half of the collarbone meets the base of the neck.
NX: The regional lymph nodes cannot be evaluated.
N0: There is no evidence of cancer in the regional lymph nodes.
N1: Cancer has spread to lymph nodes above the triangular area described above. The lymph nodes are on the same side as the primary tumor, and the cancer found in the lymph nodes is 6 centimeters (cm) or smaller.
N2: Cancer has spread to lymph nodes on both sides of the neck, above the triangular area, but the cancer is 6 cm or smaller.
N3: Cancer found in lymph nodes is larger than 6 cm or is found in lymph nodes located in the triangle.
N3a: Cancer found in the lymph nodes is larger than 6 cm.
N3b: Cancer has extended to the triangle region.
Distant metastasis. The "M" in the TNM system indicates whether the cancer has spread to other parts of the body.
MX: Distant metastasis cannot be evaluated.
M0: Cancer has not spread to other parts of the body.
M1: Cancer has spread to other parts of the body.
Cancer stage grouping
Doctors assign the stage of the cancer by combining the T, N, and M classifications.
Stage 0: A carcinoma in situ (Tis) with no spread to lymph nodes (N0) or distant metastasis (M0).
Stage IIA: A tumor that has extended beyond the nasopharynx (T2) but has not spread to lymph nodes (N0) or to distant parts of the body (M0).
Stage III: This describes a noninvasive and invasive tumor (T1 or T2) that have spread to lymph nodes (N1 or N2) but have not metastasized (M0), or it describes a larger tumor (T3) with or without nodal involvement (N0, N1, or N2) and no metastasis (M0).
Stage IVA: This describes any invasive tumor (T4) with either no lymph node involvement (N0) or spread to only a single same-sided lymph node (N1) but no metastasis (M0). It is also used for any cancer (any T) with more significant nodal involvement (N2) but no metastasis (M0).
Histologic grade (G). Doctors also describe a primary tumor by its grade, which is determined by using a microscope to examine tissue from a tumor (called a histologic examination). The doctor compares the tumor tissue with normal tissue. Histologic grade describes how closely the cancer cells resemble normal tissue under a microscope. Normal tissue contains many different types of cells grouped together, which is called differentiated. Tissue from a tumor usually has cells that look more alike each other (called poorly differentiated). Generally, the lower the grade, the better the prognosis. A tumor's grade is described using the letter "G" and a number.
GX: The grade cannot be evaluated.
G1: The cells look more like normal tissue (well differentiated).
G2: The cells are only moderately differentiated.
G3: The cells don’t resemble normal tissue (poorly differentiated).
Recurrent: Recurrent cancer is cancer that comes back after treatment. If there is a recurrence, the cancer may need to be staged again (called re-staging) using the system above.
Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual, Seventh Edition (2010) published by Springer-Verlag New York, www.cancerstaging.net.