After anal cancer is diagnosed, more tests will be performed to determine if the cancer has spread. Your doctor will then stage the cancer using those test results and the tumor, node and metastasis (TNM) staging system developed by the American Joint Committee on Cancer (AJCC). Doctors categorize the tumor (T) according to its size and location, whether cancer cells are found in nearby lymph nodes (N) and whether the cancer has metastasized (M), or spread, elsewhere in the body (see Table 1 and Table 2). The most common areas of metastasis are the liver and lungs.
Doctors also describe anal cancer by its grade (G), which describes how much cancer cells look like healthy cells when viewed under a microscope (see Table 3). If the cancer looks similar to healthy tissue and contains different cell groupings, it is called “differentiated” or a “low-grade tumor.” If the cancerous tissue looks very different from healthy tissue, it is called “poorly differentiated” or a “high-grade tumor.” The cancer’s grade may help the doctor predict how quickly the cancer will spread. In general, the lower the tumor’s grade, the better the prognosis.
Table 1. AJCC TNM System for Classifying Anal Cancer
|TX||Primary tumor not assessed.|
|T0||No evidence of primary tumor.|
|Tis||High-grade squamous intraepithelial lesion.|
|T1||Tumor not more than 2 cm.|
|T2||Tumor more than 2 cm but not more than 5 cm.|
|T3||Tumor more than 5 cm.|
|T4||Tumor of any size invading adjacent organ(s), such as the vagina, urethra or bladder.|
|NX||Regional lymph nodes cannot be assessed.|
|N0||No regional lymph node metastasis.|
Metastasis in inguinal, mesorectal, internal iliac or external iliac nodes.
Metastasis in inguinal, mesorectal or internal iliac lymph nodes.
Metastasis in external iliac lymph nodes.
Metastasis in external iliac with any N1a nodes.
|M0||No distant metastasis.|
Table 2. Anal Cancer Grades
|GX||Grade cannot be determined.|
|G1||Well differentiated (low grade).|
|G2||Moderately differentiated (low grade).|
|G3||Poorly differentiated (high grade).|
|G4||Undifferentiated (high grade).|
Table 3. Stages of Anal Cancer
|IV||Any T||Any N||M1|
*Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging System, Ninth Version (2022) published by Springer Science+Business Media.