Stomach cancer. Gastroscope (endoscope) view of a gastric tumour (adenocarcinoma) in a 40 year-old woman. An adenocarcinoma is a cancer that arises from the glandular tissue of an organ's epithelium (lining). This is a linitus plastica or leather bottle stomach, which is characterized by a thickening of the muscular wall rather than a localized lump. It tends to occur in younger patients and is more common in Japan and Scandinavian countries. Treatment involves surgical removal of part of the stomach.