Lipoma in the colon. Coloured X-ray of a lipoma (bulbous shape, lower right) in the colon (the large intestine). A lipoma is a benign tumour that forms from fat cells. Lipomas are most common in the skin, and are rare in the intestinal tract. A large lipoma can obstruct the passage of digested food through the intestine, requiring the surgical removal of the tumour. In rare cases a lipoma may turn cancerous, when it is termed a liposarcoma. Part of the spine is seen down far right.