The following tests may be carried out in a patient suspected with anal cancer -

Physical examination: During examination, the doctor examines the patient by looking at the anus. He also inserts a gloved finger into the anus to feel for any abnormality.

Ultrasound probe: The doctor inserts a tube with an ultrasound probe at the end to look out for any abnormality. He biopsies any suspicious area and sends it to a pathology laboratory for testing.

Anoscopy: The doctor may directly visualize the inner lining of the anus through an instrument inserted into the anus.

CT scan / PET scan / Ultrasound are tests carried out check if the tumor has spread to other parts of the body.
It is important to detect cancer early to prevent its spread to other areas. If a person is prone to anal cancer, the following test can be carried out -

Anal swab: The doctor takes a swab of the anus and tests the cells collected for cancer. This test can be conducted at regular intervals.
Any tissue that is removed is sent for biopsy to get the final confirmation of the cancer.