Anal Sac Adenocarcinoma

Anal sac adenocarcinoma is a cancer that arises in the tissue of the anal sacs — the small scent glands that sit just inside the anus in dogs and cats. It tends to grow locally and can spread to nearby lymph nodes and, in some cases, to more distant sites. Owners often notice scooting, licking at the rear, difficulty passing stools, or swelling to one side of the anus, though in some animals the first sign is detected during a routine examination. This condition is more common in older dogs, particularly certain breeds, and is rare in cats. The signs can be subtle early on and may overlap with more common anal sac problems, so investigation typically involves imaging and sampling of any masses or enlarged lymph nodes. This page explores what signs may be observed, what is happening in the tissue, how the condition is investigated and staged, and what treatment approaches exist. Each section is written to help you understand the landscape, not to direct a specific course.