Biopsies and imaging tests are the primary tools doctors use to diagnose anal cancer. These tests help to identify tumors, see how far the cancer has spread, and determine staging.
Anal cancer is much less common than colon cancer or rectal cancer. Most cases are linked to a human papillomavirus (HPV) infection.
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Doctors stage anal cancer from stage 0 to stage 4 depending on how far it’s spread.
Stage 0 anal cancer is considered precancerous and has the best outlook. Stage 4 anal cancer has spread to distant organs like your lungs or liver.
Read on to learn more about how anal cancer is staged and how your stage influences your treatment options and outlook.
Signs and symptoms of anal cancer
Anal cancer can cause signs and symptoms like:
- changes in your bowel habits
- anal itchiness or anal discharge
- anal pain or pressure
- a lump or bleeding around your anus
It’s important to see your doctor if you develop any of these signs or symptoms. Your doctor can help you rule out all potential causes.
The main test for anal cancer is a biopsy. This is where a small tissue sample is removed with a long, thin tube called an endoscope. The cells are then analyzed in a lab for signs of cancer.
Imaging tests can help identify tumors and see how far your cancer has spread. You may receive an imaging test such as:
- ultrasound
- computed tomography (CT) scan
- MRI
- chest X-ray, to check if it has spread to your lungs
- positron emission tomography (PET) scan
The most common staging system for anal cancer is called the American Joint Committee on Cancer (AJCC) TNM system. This system stages your cancer from stage 0 to 4 based on three factors.
- (T): The size of your Tumor
- (N): Whether your cancer has spread to lymph Nodes
- (M): Whether your cancer has Metastasized, meaning spread to distant tissues
N and M are assigned values of 0 if the cancer hasn’t grown into these areas and 1 if it has. T is assigned a value from 1 to 4 depending on the size of the tumor.
Anal cancer is divided into the following stages in the TNM staging system:
Stage 0
Stage 0 anal cancer is a precancerous growth limited to the inner lining of your anus. It’s also called a high-grade intraepithelial lesion or carcinoma in situ.
Doctors usually treat it by removing the growth and some healthy tissue around it.
Stage 1
In stage 1, your tumor is
Treatment for anal cancer in stages 1 to 3 usually consists of some combination of:
- surgery to remove the area around the tumor
- surgery to remove your anus, rectum, and lower part of your colon
- external-beam radiation therapy with chemotherapy
- radiation therapy
Stage 2
Stage 2 anal cancer is broken into stage 2A or 2B depending on how big it is. Cancer in this stage still hasn’t spread to lymph nodes or distant body parts (N0 and M0).
- It’s classified as stage 2A if your tumor is between 2 centimeters to 5 centimeters (T2).
- It’s classified at stage 2B if your tumor is larger than 5 centimeters (T3).
Stage 3
Stage 3 cancer is divided into three subcategories. Cancer in this stage may or may not have spread to lymph nodes (N0 or N1) but hasn’t spread to distant body parts.
| Stage | Description |
|---|---|
| Stage 3A | • T1: the tumor is smaller than 2 centimeters across • N1: the tumor has spread to lymph nodes near your rectum • M0: the tumor hasn’t spread to distant areas OR • T2: the tumor is between 2 and 5 centimeters across • N1: the tumor has spread to lymph nodes near your rectum • M0: the tumor hasn’t spread to distant areas |
| Stage 3B | • T4: the tumor is any size and is growing into nearby organs such as your urethra, prostate, bladder, or vagina • N0: the tumor has not spread to lymph nodes near your rectum • M0: the tumor hasn’t spread to distant areas |
| Stage 3C | • T3: the tumor is larger than 5 centimeters across • N1: the tumor has spread to lymph nodes near your rectum • M0: the tumor hasn’t spread to distant areas OR • T4: the cancer is any size and is growing into nearby organs such as your urethra, prostate, bladder, or vagina • N1: the tumor has spread to lymph nodes near your rectum • M0: the tumor hasn’t spread to distant areas |
Stage 4
Anal cancer is classified as stage 4 if it has spread to distant organs (M1). The tumor can be any size and it may or may not have grown into nearby lymph nodes (any T and any N).
Stage 4 anal cancer treatment is often palliative, meaning the goal is to improve your quality of life and symptoms. Treatment options include:
- palliative surgery
- palliative radiation therapy with or without chemotherapy
- palliative chemotherapy alone
- a clinical trial of immune checkpoint inhibitors or newer treatments
The 5-year relative survival rate is a measure of how many people with the cancer survive at least 5 years compared to a person in the general population.
People with anal cancer had the following
| Stage | 5-year relative survival rate |
|---|---|
| Localized (stage 1) | 82% |
| Regional (stage 2 or 3) | 66% |
| Distant (stage 4) | 35% |
| All stages | 69% |
Factors linked to better survival include:
- smaller tumor size
- cancer that hasn’t spread to lymph nodes
- normal levels of hemoglobin
- squamous cell carcinoma cancer type
Anal cancer is staged from stage 0 to stage 4 depending on how far cancer has spread. It has the best outlook when it’s caught early.
Anal cancer can often be treated with some combination of surgery, chemotherapy, or radiation therapy. Treatment for stage 4 anal cancer often focuses on minimizing your symptoms and maximizing your quality of life.