A Giant Lipoma Presenting with Colocolonic Invagination

Abstract

Turkish Abstract

Introduction

Colonic lipomas are rare benign mesenchymal tumors of gastrointestinal system which have an incidence ranging from 0.15% to 4.4%¹. Most of these lipomas are asymptomatic, however the symptoms may vary according to size, location and structural features of lipomas. Large-sized lipomas are often misdiagnosed as malignant tumors and may require immediate surgical intervention if they cause obstruction and invagination^1-3. Remaining colonic lipomas in differential diagnosis and appropriate radiological evaluation can prevent unnecessary extensive surgical resections.

Case Report

A 55-year-old male patient presented with a history of abdominal pain, anorexia, nausea, vomiting and abdominal swelling. Ultrasonographic examination showed colocolonic invagination at hepatic flexure which caused by a hypoechoic mass lesion with a diameter of 4.5x6.5x7 cm. Abdominal computerized tomography (CT) revealed a smooth and oval-shaped hypodense lesion, with a fat equivalent density (Figure 1).

Figure 1 CT scan showed a smooth and oval-shaped hypodense mass of fat density which caused intussusception of the ascending colon into transverse colon.

On T2-weighted and fat-suppressed magnetic resonance imaging (MRI), an ovoid mass similar to fat signal intensity was observed in the proximal transverse colon as shown in Figure 2.

Figure 2 On T2-weighted (A) and fat-suppressed (B) MRI, an ovoid mass similar to fat signal intensity was observed in the proximal transverse colon

The radiological findings supported the diagnosis of colonic lipoma. Colonoscopy revealed that the giant intussuscepted mobile lesion had a large pedicle with a heterogeneous appearance with overlying necrosing mucosa. Surgical operation was performed. Diagnosis of colonic lipoma  was established based on the  histopathologic examination of the  specimen (Figure 3).

Figure 3 Macroscopic assessment of the resected specimen showed the presence of a round pedunculated colonic polipoid submucosal tumor which served as a lead point for the invagination

Discussion

Invaginations in adullts are very rare and more than 90% of them are associated with a mass as a leading point which is malignant in 60% cases ^4,5. Jain R et al. in 2016 reported  that the number of intussuscepted lipomas was only 50 in the literature ⁴.

Colonic lipomas larger than 4 cm are called as giant lipomas and approximately 75% of them are symptomatic¹.  These symptoms which can be easily confused with colon malignancies are abdominal pain, rectal bleeding, anemia, constipation, weight loss, intestinal obstruction or invagination-related ileus, and these findings ^1-6.

On CT scan images, lipomas have a smooth border appearance with a fat equivalent density that ranges from -50 to -150 Hounsfield unit ^2,5,7. MRI especially is able to detect fatty lesions because of typical signal intensity characteristics for adipose tissue mainly on T1-weighted and fat-suppressed images ^3,5-7.

Although,  colonoscopy is reliable in the diagnosis of classical lipomas, sometimes the differential diagnosis of giant lipomas with malignancy is not clear and it can be definitively diagnosed by histopathologic examination of the specimen ^1-6..

In conclusion, giant colonic lipomas may present difficulties because of their unusual clinical findings in pre-operative differentiation between malignant and benign colonic neoplasms. Colonic lipomas should always be considered in the differential diagnosis and appropriate radiological imaging can be helpful to avoid unnecessary extensive surgical resections.

References

1. Dandin Ö, ve ark.  Nadir bir karın ağrısı ve anemi nedeni: dev kolonik lipom. Kolon Rektum Hast Derg.  2011;21:116-9.
2. Aytaç B, Yerci Ö, Gürel S, Ferik Z. Colonic lipomas mimicking colon cancer. Turkish Journal of Pathology.  2010;26(3):196-9.
3. Yaman İ, Derici H, Demirpolat G. Dev kolon lipomu: olgu sunumu. Ulusal Cer Derg.  2014;30.103-5.
4. Jain R, et al.  Adult sigmoid colocolic intussusception due to polypoidal lipoma. A Rare Case Report.  Br J Med Med Res. 2016;18(5):1-4.
5. Mouaqit O, et al.  Pedunculated lipoma causing colocolonic intussusception: a rare case report. BMC Surgery.  2013, 13:51.
6. Şenyürek G, Yürüker SS, Koca B, Karabıçak İ, Özen N. Transvers kolonda yerleşmiş dev submukozal lipom olgusu eşliğinde literatür taraması. Göztepe Tıp Dergisi. 2013;28(3):147-9.
7. Tüzün M, Hekimoğlu B. Lipomların nadir lokalizasyonları: BT ve MR görünümleri. Türk Radyoloji Derg.  2016;35:77-80.

Information Presentation

TRD 38. Ulusal Radyoloji Kongresi, 31 Ekim-4 Kasım 2017 Sueno Belek Kongre Merkezi, Antalya

 (Bildiri poster olarak kabul edildi)