The staging process involves determining the extent of the cancer for
treatment and prognosis (likely outcome) purposes. The most common
system used for thyroid cancer staging is the TNM system of the American Joint
Committee on Cancer (AJCC; in conjunction with an international cancer
committee).
T = Tumor size
N = Node involvement
M = Metastasis situation
Those letters are combined with other numbers and letters to indicate
severity and combinations. The system looks like this:
The classifications for T:
TX: Primary tumor cannot be assessed (information unavailable)
T0: No evidence of primary tumor
T1: The tumor is 2 cm or smaller
T2: Tumor is between 2 cm and 4 cm
T3: Tumor is larger than 4 cm or has slightly grown outside the
thyroid
T4a: Tumor of any size and has grown beyond the thyroid gland to
invade nearby tissues
T4b: Tumor has grown into the spine or into nearby large blood
vessels
The classifications for N:
NX: Regional (nearby) lymph nodes cannot be assessed
N0: No regional lymph node spread
N1: Spread to lymph nodes
N1a: Spread to lymph nodes in the neck (cervical lymph nodes)
N1b: Spread to lymph nodes in the upper chest (upper mediastinal
lymph nodes)
The classifications for M:
MX: Presence of distant metastasis (spread) cannot be assessed
M0: No distant metastasis
M1: Distant metastasis is present, involving nonregional lymph nodes,
internal organs, bones, etc.
Stage grouping consists of combining several TNM
descriptions into more distinct stages. While most other cancers are
stage-grouped, thyroid cancer is different in that it is grouped into
categories that take in to account the type of cancer and the patient’s age.
Other cancers tend to be generalized. (The following chart portion is taken
from the American Cancer Society at www.cancer.org)