Gastrointestinal: Gastrointestinal lipomas

Abstract

Lipomas are benign tumors composed of multiple discrete masses of fat separated by thin fibrous septa. In the gastrointestinal tract, at least 70% of lipomas are located in the large bowel but other sites include the small bowel (25%) and stomach (5%). In the large bowel, the majority of lipomas are located in the cecum and ascending colon. However, true lipomas close to the ileocecal valve need to be distinguished from fatty infiltration of the valve, a common disorder which is sometimes called lipohyperplasia. Lipomas are usually solitary but vary widely in size, shape and consistency. Some are sessile nodules that project into the bowel lumen while others are polypoid tumors that are largely intraluminal. A characteristic feature is a shiny, yellowish lesion covered by normal mucosa. In relation to consistency, some are firm, others are spongy with a ‘pillow cushion sign’ and a minority are soft and flaccid, particularly those in the stomach. Most lipomas are asymptomatic. However, larger lesions can ulcerate and bleed and there are case reports of partial or complete bowel obstruction, sometimes with intussusception. The patient whose images are shown in Figure 1 was a 40-year-old woman who had a colonoscopy because of episodes of lower abdominal pain. A large polyp, approximately 4 cm in diameter, with surface ulceration was identified in the region of the hepatic flexure. As biopsies were inconclusive, a right hemicolectomy was performed that revealed an elongated tumor, 5.5 cm × 3 cm in size, with apical ulceration. Histological evaluation revealed typical features of a lipoma. The image in Fig. 2 was a polypoid lesion in the transverse colon. The lesion was identified as a probable lipoma because of the smooth, shiny surface with yellowish coloration. The polyp was resected by loop diathermy and had typical histological features of a lipoma. Care should be taken with the endoscopic resection of sessile lipomas as there appear to be significant risks for colonic perforation and bleeding.