Mesenteric lipoma is a benign mesenchymal tumor arising from mesenteric fat tissue, composed of mature adipocytes. It is the most common benign mesenchymal tumor of the gastrointestinal system. Usually asymptomatic and discovered incidentally; large lesions may become symptomatic through mechanical compression, intussusception, or rarely torsion. Can occur at any age but peaks in adults aged 40-60 years. Homogeneous fat density between -80 and -120 HU on CT is specific enough for pathological diagnosis. On MRI, it shows high signal on both T1 and T2 and signal completely drops with fat suppression — this finding confirms benign lipoma diagnosis. It may contain thin septa or feeding vessels, but absence of solid component or enhancing focus distinguishes from liposarcoma. Surgical excision is curative for symptomatic lesions and recurrence is not expected.
Age Range
30-70
Peak Age
55
Gender
Equal
Prevalence
Uncommon
Mesenteric lipoma is a benign tumor arising from mature adipocytes in the mesentery. Adipocytes display normal fat metabolism; a single large lipid droplet is present within the cell and the nucleus is pushed to the periphery. The tumor grows slowly and forms a thin fibrous capsule — this capsule makes the lesion margins distinct on CT and MRI. Homogeneous fat density (-80 to -120 HU) results from the triglyceride content of mature adipocytes significantly reducing X-ray attenuation. On MRI, the short T1 relaxation time of fat protons causes T1 hyperintensity, while high proton density causes T2 hyperintensity. In fat suppression sequences, frequency-selective saturation eliminates fat proton signal and the lipoma signal completely drops. Unlike liposarcoma, lipoma has no dedifferentiation, myxoid transformation, or neovascularization — therefore no enhancing solid component is present. Rare complications include pedunculated lipomas causing intussusception and giant lipomas compressing adjacent structures.
Homogeneous fat density between -80 and -120 HU on CT, well-defined, encapsulated mesenteric mass — combined with absence of solid component or enhancement, pathognomonic for lipoma diagnosis.
On non-contrast CT, a well-defined, oval or round mass with homogeneous fat density between -80 and -120 HU within the mesentery. Thin capsule may show slightly higher density than surrounding mesenteric fat. Thin septa (<2 mm) may be present but no solid nodular component. Calcification, necrosis, and hemorrhage are typically absent.
Report Sentence
A well-defined, encapsulated mass measuring approximately ... cm with homogeneous fat density (-... HU) is seen within the mesentery; consistent with mesenteric lipoma.
Homogeneous hyperintense signal at the same level as subcutaneous fat on T1-weighted images. Capsule and thin septa are seen as hypointense linear structures on T1. Signal completely drops on fat-suppressed T1 sequence — this finding is pathognomonic for lipoma diagnosis and distinguishes from the solid component of liposarcoma.
Report Sentence
The mesenteric mass shows homogeneous hyperintense signal at the same level as subcutaneous fat on T1-weighted sequence with complete signal drop on fat suppression; consistent with benign lipoma.
On T2-weighted images, the lesion shows moderate to high hyperintense signal. Signal completely drops on fat-suppressed T2 (STIR) sequence — this confirms the pure fat content of the lesion. Thin septa may be mildly hyperintense on T2 and may show minimal post-contrast enhancement.
Report Sentence
The mass shows hyperintense signal on T2-weighted sequence with complete signal drop on STIR sequence; consistent with pure fat content supporting lipoma diagnosis.
On post-contrast CT, the lesion shows no enhancement — fat density remains unchanged. Thin capsule and septa may show minimal enhancement, but no solid nodular enhancing component is present. This finding reflects the avascular mature adipocyte structure of lipoma and clearly distinguishes from the enhancing solid component of liposarcoma.
Report Sentence
The mass shows no post-contrast enhancement; no solid component or enhancing nodular focus is seen — consistent with benign lipoma.
On US, a homogeneous echogenic (hyperechoic), well-defined, oval mass. Internal structure is homogeneous without anechoic cystic component. Posterior acoustic shadow is usually absent. Vascularity is minimal or absent on Doppler. Large lipomas may displace surrounding structures but no evidence of invasion.
Report Sentence
A homogeneous echogenic, well-defined, oval mass is seen within the mesentery; no vascularity on Doppler — consistent with lipoma.
Prominent India ink artifact (chemical shift artifact) is seen at the margins of the lipoma on opposed-phase images — signal loss at fat-water interface. No signal loss within the lipoma internal structure because the lesion is pure fat (no intravoxel fat-water mixture). This finding demonstrates the pure fat content of lipoma and sharp boundary from surrounding tissue.
Report Sentence
India ink artifact is seen at the mass margins on opposed-phase images; no signal loss within the internal structure — consistent with pure fat content lipoma.
Criteria
Most common type. Homogeneous fat density, thin capsule, no or minimal septa. No post-contrast enhancement. No further workup needed.
Distinct Features
Uniform density between -80 and -120 HU on CT; signal parallel to subcutaneous fat on all MRI sequences; complete signal loss with fat suppression.
Criteria
Lipoma containing thin septa (<2 mm). Septa may show minimal post-contrast enhancement. Septa should not be thick (>2 mm) or nodular to differentiate from liposarcoma.
Distinct Features
Thin linear enhancing septa areas on CT; fat density compartments same as lipoma. Septa are T2 hyperintense on MRI with thin linear post-contrast enhancement.
Criteria
Lesions >10 cm. Mechanical compression symptoms (abdominal pain, obstruction) common. Surgical resection usually necessary. Differential diagnosis from liposarcoma should be carefully evaluated.
Distinct Features
Displaces adjacent structures due to large size; if homogeneous fat density/signal is preserved on CT and MRI, evaluated in favor of benign lipoma; any solid/enhancing component should rule out liposarcoma.
Distinguishing Feature
Liposarcoma contains thick septa (>2 mm), nodular enhancing solid component and heterogeneous density (soft tissue components); lipoma has homogeneous fat density and no solid component.
Distinguishing Feature
Lymphoma is a soft tissue density (20-40 HU), homogeneously enhancing mass without fat density; lipoma has -80 to -120 HU homogeneous fat density.
Distinguishing Feature
Sclerosing mesenteritis shows hazy density increase (misty mesentery) and fat ring sign in mesenteric fat; lipoma has homogeneous fat density and no density increase in surrounding fat.
Distinguishing Feature
Mesenteric cyst is a thin-walled, cystic lesion at water density (0-20 HU); lipoma is a solid mass at fat density (-80 to -120 HU).
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
no-follow-upMesenteric lipoma is a benign lesion and biopsy is not needed because homogeneous fat density on CT is diagnostic. No follow-up or treatment is needed for asymptomatic lesions. Surgical excision is curative for symptomatic lesions (compression, obstruction, intussusception) and recurrence is extremely rare. In the presence of any solid, enhancing, or heterogeneous component on CT, liposarcoma should be excluded and biopsy/surgery should be considered.
Mesenteric lipomas are benign lesions that generally require no treatment. Large lesions may cause bowel obstruction. Absence of soft tissue component should be confirmed to exclude liposarcoma. Follow-up is generally not needed.