Anal cancer

Anal cancer is a malignant tumor arising in the anal canal or anus. Most cases are squamous cell carcinomas, often associated with persistent infection by high-risk human papillomavirus.

Human papillomavirus: A group of viruses that infect skin and mucous membranes; persistent infection with some types can cause cancer. Persistent high-risk HPV infection drives most anal squamous cell cancers.
Anoscopy: Examination of the anal canal using a short, rigid viewing instrument. It allows clinicians to inspect suspicious anal lesions and guide biopsy.
Rectal cancer: Cancer arising in the rectum, the final section of the large intestine before the anal canal. Its location, typical biology, and treatment differ from those of anal cancer.
Anal cancer screening: Testing people without symptoms to detect anal precancer or cancer before clinical signs appear. Screening strategies target groups at elevated risk, though routine population screening is not established.
Anal intraepithelial neoplasia: Abnormal growth of squamous cells in the anal lining that can precede invasive cancer. This precancerous change can progress to anal squamous cell carcinoma.
Biopsy: Removal of tissue for examination to diagnose disease, including cancer. Microscopic examination of a biopsy confirms whether an anal lesion is cancerous.
Anal adenocarcinoma: A rare anal cancer arising from glandular cells rather than squamous cells. It is a distinct, uncommon histology compared with the usual squamous cell type.
Anal cytology: Microscopic examination of cells collected from the anal canal to detect abnormalities. It is used in some high-risk groups to identify anal precancerous changes.
Anal canal: The terminal portion of the digestive tract between the rectum and the anal opening. Most anal cancers arise in its lining, where tumor location affects classification and treatment.
Cancer staging: Classification of a cancer's extent, including tumor size and spread to lymph nodes or distant organs. Staging guides treatment by describing how far anal cancer has spread.

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