Large Colonic Lipomas

Lipomas are common, nonepithelial, benign, fatty tumors that can be found throughout the gastrointestinal tract, although they are most frequently seen in the colon. Approximately 90% of colonic lipomas are located in the submucosa; the remainder of these tumors are subserosal or intramucosal in origin. The reported incidence of colonic lipomas ranges from 0.2% to 4.4%.¹ Lipomas of the large intestine are most commonly seen (in order of decreasing frequency) in the cecum, ascending colon, and sigmoid colon. Of note, more than 70% of these tumors are located in the right hemicolon. Colonic lipomas are more common in women than in men, with a predilection for the right colon in women and the left colon in men. The mean age of patients with colonic lipomas falls within the sixth decade. Colonic lipomas vary in size from several millimeters to 30 cm. Lipomas are usually well-delineated, soft, ovoid, yellowish masses. These tumors can be found by themselves or in groups, and they can be sessile or pedunculated.^2,3 Several cases of primary colonic liposarcomas have been reported in the literature, whereas other lipomas are mostly seen in conjunction with retro-peritoneal liposarcomas.⁴

Presentation

Colonic lipomas are generally asymptomatic and are found incidentally during a colonoscopy or surgery for other conditions. Symptoms correlate with the size of the lipoma; lipomas larger than 4 cm in size become symptomatic in 75% of patients.^5,6 Lipomas often present with vague symptoms—such as abdominal pain and/or alterations in bowel habits—and rarely manifest as gastrointestinal bleeding, perforation, or obstruction.⁷ Giant lipomas (>4 cm) are the most common benign tumors in the colon that cause intussusception, although no specific incidence data have been documented.⁸ Even patients with large lipomas may have nonspecific or intermittent symptoms, which causes delay and difficulty in making the diagnosis. Intussusceptions are usually limited to 1 segment of the colon—either ascending, transverse, or descending—but can extend to more than 1 segment in some cases.⁹ Large lipomas may develop superficial ulceration and bleeding and may present with a combination of symptoms.¹⁰ Due to similarities in age and symptoms, colonic lipomas may mimic malignancy in presentation.

Gould and associates present a case of a colonic lipoma that meets the typical age, gender, and symptoms of this tumor but not the typical location or appearance; the patient had a large mass with atypical characteristics (ulceration) on gross examination, an atypical site, and development of intussusception.¹⁰

Characteristic radiographic findings—detected via barium enema, computed tomography scan, or magnetic resonance imaging—and endoscopic findings—as described in the case study by Gould and coworkers—are useful in the diagnosis of a typical lipoma.¹⁰ However, the presence of intussception, irregular margins, lymph node enlargement, or thickening of the bowel wall—in association with a mass seen on imaging—raises suspicion for a malignant etiology.¹¹ Similarly, colonoscopic findings— such as the presence of a firm or fungating mass, ulceration, or necrosis—are concerning for malignancy.¹² Even experienced endoscopists may mistake a large colonic lipoma for a large polyp or colorectal cancer (Figure 1).

Figure 1.

A large colonic lipoma that was initially thought to represent a primary colorectal cancer. The lesion was subsequently removed endoscopically without difficulty.

Endoscopic ultrasound (EUS) has been used to assist in the diagnosis of colonic lipomas. EUS typically demonstrates a hyperechoic lesion originating in the submucosal layer that is diagnostic for lipoma. Lipomas with an atypical heterogeneous or hypoechoic appearance on EUS have been documented in the literature.¹³ Giant lipomas may undergo intermittent torsion and ischemia, causing inflammatory changes in the surrounding mucosa and thus altering their appearance on endoscopy. Histopathologic analysis is required for definitive diagnosis in such settings and is often attained after surgical or endoscopic resection of the tumor.¹⁴

Management

Colonic lipomas that cause symptoms or pose a diagnostic dilemma, as in the case study reported by Gould and associates, should undergo evaluation with an eye toward resection.¹⁰ Both surgical and endoscopic techniques have been widely used in the management of colonic lipomas, although no consensus is available regarding which procedure takes precedence. Surgical therapy is more commonly used for large lesions, as in the case study by Gould and coworkers.¹⁰ As lipomas show no significant malignant degeneration, small (<2 cm) asymptomatic lipomas can be observed when unequivocally proven by biopsy or imaging to have typical findings on EUS. In the past, endoscopic resection has been thought to be associated with a higher risk of perforation and bleeding, but multiple case reports have recently demonstrated good success rates and acceptable complication rates.^15,16 Because the vasculature, size, and extension of the muscularis propria or serosa into the pedicle determines the outcome of endoscopic resection, a detailed examination of the base of the lipoma during endoscopy guides decision-making regarding surgical versus endoscopic resection.¹⁷ EUS can be valuable for obtaining such details and minimizing complications of endoscopic removal.¹⁸ Pedunculated lipomas up to 11 cm in size have been safely removed endoscopically via newer techniques, such as snare electrosurgery or endoloop ligation.^19,20

Surgical resection is the treatment of choice when giant lipomas are complicated by intussusception or bowel obstruction. Surgical resection should also be the first-line management for lipomas that are sessile, have limited peduncles, or have extension of serosa/muscularis propria into the pedicle. When attempted endoscopic resection fails, large lipomas should be removed surgically. Various surgical techniques—such as hemicolectomy, segmental resection of the involved colon, or local excision—have all been used with success. However, local excision should be considered whenever feasible in order to limit morbidity.^21,22

The patient in the case study by Gould and colleagues was appropriately managed by surgical resection of the colonic segment containing the mass and intussus-ception.¹⁰ Based upon histopathology, the resected mass was later found to be a lipoma.

Outcome

Spontaneous expulsion of lipomas secondary to autoamputation has been reported in the literature.²³ Both surgical and endoscopic resection of colonic lipomas show good outcomes with no known recurrence after complete removal.¹⁸ The key take-home message should be that while most colonic lipomas are small and asymptomatic, larger lesions may mimic polyps or tumors, cause a variety of symptoms, and warrant surgery.