Intestinal fat tumour. Gross specimen of a lipoma (round lump) in the small intestine. A lipoma is a tumour that forms from fat cells. Lipomas are most common in the skin, and are rare in the intestinal tract. The growth of the tumour can obstruct the intestine, requiring the surgical removal of the tumour. In rare cases a lipoma may turn cancerous, when it is termed a liposarcoma.