Lipomas are soft tissue tumors deriving from the proliferation of mature adipocytes. They are found most commonly in the colon, but may develop in any part of the gastrointestinal tract.^1-3 Colonic lipomas are usually benign neoplasms that are asymptomatic and detected incidentally at radiological investigation, colonoscopy, surgery or autopsy. Lesions larger than 2 cm may present with abdominal pain, changes in bowel habits, bleeding, intussusception or bowel obstruction.^1-3

Autoamputation of polypoid lesions in gastrointestinal tract is an extremely rare phenomenon.^4-10 But the precise mechanism of the phenomenon remains unknown. It presumably occurs because of ischemic necrosis of polyp by peristalsis induced torsion or tension.^4-10

We, herein, report a case of autoamputation of giant colonic lipoma in a 48-year-old man and review the literature pertaining to this condition.

A 48-year-old man was admitted to Chonnam National University Hwasun Hospital with 3-month history of abdominal discomfort caused by positional change. Three years ago, he underwent surgery for advanced gastric cancer. On admission, his abdomen was soft and non tender, but a movable huge mass was detected on rectal examination. All laboratory examinations including complete peripheral blood cell counts, blood biochemistry and carcinoembryonic antigen were within normal range. Colonoscopy revealed a huge movable mass with a diameter of 8 cm, covered by focally ulceration and hemorrhagic mucosa in the distal rectum (Fig. 1A) remnant long stalk with necrotic and ulcerative tissue the in transverse colon (Fig. 1B). We resected a remnant long stalk by a standardized technique of snare polypectomy after injection of the base with epinephrine or saline solution (Fig. 1C and D). And a huge movable mass in the rectum was completely removed after fragmentation of mass using polypectomy snare (Fig. 2A and B). There was no procedure-related complication. Histopathologic examinations of huge mass and remnant stalk revealed normal mature adipocytes compatible with those of lipoma (Fig. 3). His symptom disappeared soon after removal of colonic lipoma and he remains asymptomatic.

Most colonic lipomas are asymptomatic but may cause abdominal pain, bowel habit changes, gastrointestinal bleeding, perforation, intussusception or bowel obstruction according to size and location.^1-3

Autoamputation of colonic lipoma is indeed rare clinical presentation.^4-10 The underlying mechanisms of this presentation are still poorly understood. Several mechanisms have been hypothesized. This unusual presentation may follow twisting of the pedicle/stalk, ulcerogenic medications, or necrosis and cancerous infiltration of the polyp base. Torsion or tension may result in twisting polyp, causing ischemic necrosis and tearing of the polyp base or amputation. Especially, pedunculated polyps may be easily distorted and are subjected to mechanical tension.^4-10 In our case, colonoscopy revealed a huge movable mass with focally ulceration and hemorrhagic mucosa in the rectum and remnant long stalk with necrotic and ulcerative tissue on the transverse colon. Therefore, although not observe the polyp just before autoamputation, we believe that the large pedunculated polyp had undergone extensive ischemic necrosis possibly as a consequence of torsion induced by peristalsis, and autoamputation had undergone.

According to previous reports, significant complications associated with autoamputation of gastrointestinal polypoid lesions include intussusceptions, gastrointestinal bleeding and perforation.^4-10 Fortunately, our case had no significant complication.

The treatments of a remnant lesion after autoamputation of colonic lipoma include observation, surgical resection and endoscopic treatment.¹⁰ The decision to resect a remnant lesion should be based on clinical judgement about further complications and associated diseases. So, colonoscopic evaluation is necessary not only to determine the size and location of a remnant lesion but also to identify another lesions including coexistence of cancers. In our case, we resected a remnant long stalk located in transverse colon by injection-assisted snare polypectomy. And an autoamputated lipoma mass in the rectum was completely removed after fragmentation of mass using polypectomy snare through intermittent electric current carefully during 100 minutes. There was no procedure-related complication. To our knowledge, autoamputation is rare and endoscopic treatments for such lesions have been not reported before.

Although reported for successful endoscopic removal of colonic lipoma by EUS guiding, injection of epinephrine-saline mixed solution on base of lipoma and using by detachable snare, usually pedunculated type, the endoscopic resection of colonic lipomas is limited because the fatty tissue is inefficient conductor for electronic current and may result in a high rate of complications including perforation and hemorrhage.^11-14 Currently, surgical resection should be preferred when lesion is large sessile or broadly-based, can not rule out malignancy, causes significant symptoms including intussusception, or is involved in the propria muscle or serosal layer.^15-18

In conclusion, autoamputation of gastrointestinal polypoid lesions presumably occurs because peristalsis induced torsion or tension on pedicle/stalk can cause ischemic necrosis of polyp base and subsequently sloughing of polyp. Autoamputation should be considered as a rare clinical manifestation of colonic lipoma. Injection-assisted snare polypectomy technique may be useful for removal of colonic lipoma according to clinical judgement.