Lipoma of the greater omentum is an extremely rare benign abdominal childhood tumor, with only nine previous reports in the literature 1–9. We report a giant omental lipoma in a 21-month-old girl that was completely excised. This also involved resection of a part of the spleen.
A 21-month-old girl weighing 12 kg presented with a history of progressive, painless abdominal distension for the past 2 months. A nontender, firm, lobulated mass occupying most of the left half of the abdomen and also crossing the midline was palpable. The fingers could not be insinuated between the left costal margin and the mass. The mass had side-to-side mobility and was bimanually palpable. There was a 3×2 cm café au lait patch over the swelling. A plain radiograph of the abdomen showed a homogenous ground-glass appearance on the left side of the abdomen with no calcification. Ultrasonograph (USG) suggested a large retroperitoneal noncystic mass displacing the left kidney posteroinferiorly. Serum α fetoprotein level was 1.9 ng/ml (<5 ng/ml normal value). Contrast-enhanced computed tomography (CT) scan of the abdomen indicated a large well-defined intraperitoneal lesion with a predominant fat component (−80 to 100 HU) with multiple septa within (Fig. 1). Laterally, it abutted the abdominal wall and posterosuperiorly it was related to the pancreas. The splenic vein was compressed by the mass and it had displaced the superior mesenteric vessels to the right. There was no retroperitoneal lymphadenopathy or ascites. The absence of calcification on CT, normal α fetoprotein, and presence of a normal kidney and adrenals negated the diagnosis of teratoma, hepatoblastoma, nephroblastoma, and a cystic neuroblastoma. Thus, other tumor markers were not measured. A provisional diagnosis of omental lipoma was made on the basis of the characteristic fat attenuation on CT. Biopsy was not performed because the mobile, well-defined nature of the mass indicated a benign resectable lesion. At laparotomy, a lobulated, yellowish tumor measuring 20×14×9 cm arising from the greater omentum and occupying the intraperitoneal compartment as well as the lesser sac was found (Fig. 2). It was also attached to the tip of the lower pole of the spleen, which had to be excised. The tumor weighing 2 kg was removed in toto. Histopathological examination showed a well-encapsulated tumor composed of mature adipocytes. There were no atypical lipoblasts, increased vascularity, or myxoid changes.
The patient had an uneventful recovery and was discharged from the hospital on the fifth postoperative day. She remains asymptomatic at the 12-month follow-up, with no evidence of recurrence on follow-up USG.
Intraperitoneal lipomas are rare in childhood. Only seven cases have been reported so far arising from the greater omentum 1–7. When cases of lipoblastomas are added, the tally comes to about nine cases 7–9. These presented from the age of 9 months to 13 years 1–9 (Table 1). No sex predilection has been noted so far. There is gradual abdominal distension or a palpable lump 1,4–9. Early satiety, vomiting, and abdominal pain owing to pressure effects on surrounding structures or an emergent presentation because of torsion or partial intestinal obstruction have been reported 2,3,9,12.
The differential diagnosis includes teratoma, lymphangioma, lymphoma, alimentary tract duplications, and neuroblastoma. Lipomas are homogeneous, highly echogenic, and encapsulated on USG. A lymphoma is usually hypoechoic and a neuroblastoma is often highly echogenic. Another close differential is lipoblastoma, which appears as a well-defined hypoechoic myxoid mass embedded within highly echogenic fat 13. Identification of fat with CT is on the basis of an attenuation of less than ∼20 HU. Other lesions with predominant macroscopic fat include teratoma, myelolipoma, angiomyolipoma, liposarcoma, lipoma, epiploic appendagitis, and omental infarction 11.
The histology in lipoma will show lobules of mature adipocytes, whereas in lipoblastoma, the cells will range from immature lipoblasts to mature adipocytes and the cells may be separated by fibrous septa 10. The absence of calcification on CT, normal α fetoprotein, and presence of a normal kidney and adrenals negated the diagnosis of teratoma, hepatoblastoma, nephroblastoma, and a cystic neuroblastoma 1–9.
The recurrence rate for any lipoma after local excision is less than 5% 9. Incomplete excision and lipoblastomatosis are associated with increased chances of recurrence, about 14–20% 8. Despite its rarity, the diagnosis of omental lipoma can be made preoperatively by a careful clinical examination and appraisal of the contrast-enhanced CT scan.
Conflicts of interest
There are no conflicts of interest.
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