Adenocarcinoma is a malignant tumor originating in the glandular and epithelial tissue (the lining of the internal organs). This type of malignant tumor growth can take place in many parts of the body, including the gastrointestinal system of dogs. It may invade any part of the gastrointestinal system, including the stomach, the small and large intestine, and rectal. It commonly affects older dogs, usually more than six years of age. No particular breed is known to be predisposed and it is more common in male dogs than females. This type of cancer usually has a poor prognosis.

Lucy was diagnosed in February of 2011 and lived until July of 2011. She suffered with rectum bleeding and a slow mobility, as she got sicker. This cancer is rare in female dogs.