How is anal cancer staged?
Staging is the process of finding out how far a cancer has spread. This is important because treatment options and outlook for recovery and survival depend on the cancer's stage. If you have anal cancer, ask your cancer care team to explain the staging in a way that you understand. Knowing all you can about staging lets you take a more active role in making informed decisions about your treatment.
The tests described in the section, “How is anal cancer diagnosed?” are the ones used to determine the stage of the cancer.
Staging of anal cancer uses a system created by the American Joint Committee on Cancer (AJCC). The staging description that follows applies only to tumors in the anal canal, not to cancers that involve only the anal margin or perianal skin.
The TNM system
The TNM system for staging contains 3 key pieces of information:
- T describes the size of the primary tumor, measured in centimeters (cm), and whether the cancer has spread to organs next to the tumor.
- N describes the extent of spread to nearby (regional) lymph nodes.
- M indicates whether the cancer has metastasized (spread) to other organs of the body.
Numbers or letters appear after T, N, and M to provide more details about each of these factors:
- The numbers 0 through 4 indicate increasing severity.
- The letter X means "cannot be assessed" because the information is not available.
- The letters "is" mean "carcinoma in situ," which means the tumor is contained within the top layer of anal tissue and has not yet reached deeper layers of tissue.
T categories for anal cancer
TX: Primary tumor cannot be assessed
T0: No evidence of primary tumor
Tis: Carcinoma in situ
T1: The tumor is 2 cm (about 4/5 inch) across or smaller
T2: Tumor is between 2 and 5 cm in size (about 1 to 2 inches).
T3: Tumor is larger than 5 cm.
T4: Tumor of any size that is growing into nearby organ(s), such as the vagina, urethra (the tube that carries urine out of the bladder), prostate gland, or bladder
N categories for anal cancer
NX: Regional lymph nodes cannot be assessed
N0: No regional lymph node spread
N1: Spread to lymph nodes near the rectum
N2: Spread to lymph nodes on one side of the groin and/or pelvis
N3: Spread to lymph nodes near the rectum and in the pelvis or groin, or to both sides of the groin or pelvis
M categories for anal cancer
M0: No distant spread
M1: Distant spread to internal organs or lymph nodes of the abdomen
To make this information more helpful, these TNM descriptions can be grouped together into a simpler set of stages, labeled stage 0 through stage IV.
Stage 0: Tis, N0, M0: Stage 0 is very early cancer (or pre-cancer) that exists only in the top layer of anal tissue. This stage is also known as carcinoma in situ.
Stage I: T1, N0, M0: The cancer cells have spread beyond the top layer of anal tissue and is no longer carcinoma in situ. The tumor is less than 2 cm (about 4/5 inch) in size. It has not spread to lymph nodes or distant sites.
Stage II: T2 or 3, N0, M0: The cancer is larger than 2 cm in size, but it has not spread to nearby organs or lymph nodes. It has not spread to distant sites.
Stage IIIA: (T1-3, N1, M0) or (T4, N0, M0): The cancer can be any size and either has spread to the lymph nodes around the rectum(N1), or it has grown into nearby organs (T4), such as the vagina or the bladder without spreading to nearby lymph nodes. It has not spread to distant sites.
Stage IIIB: (T4, N1, M0), or (Any T, N2-3, M0): Either the cancer has grown into nearby organs, such as the vagina or the bladder, and has also spread to lymph nodes around the rectum, or it can be of any size but has spread to lymph nodes in the groin, with or without spread to lymph nodes around the rectum. It has not spread to distant sites.
Stage IV: Any T, Any N, M1: The cancer has spread to distant organs or tissues. It can be any size and may or may not have spread to lymph nodes.
Last Medical Review: 01/02/2013
Last Revised: 01/02/2013