Hepatic lipomas are uncommon benign lesions of the liver.
As with lipomas elsewhere in the body, hepatic lipomas are marginated masses that are composed of mature adipocytes without evidence of cellular atypia.
Histopathologic evaluation may reveal adenomatous, angiomatous, or myomatous tissue components, which may then yield a classification of "adenolipoma", "angiomyolipoma", or "myelolipoma" .
As with other lipomas, hepatic lipomas are characteristically circumscribed homogenous lesions that appear to contain macroscopic fat. They are usually isolated and range from 1 to 6 cm in diameter .
- circumscribed, solid hyperechoic mass with variable posterior acoustic shadow
- discontinuous diaphragm appearance
- refractive artifact may result in focal displacement and discontinuous appearance of the diaphragm posterior to the lipoma
- due to slower sound speed in fat tissue compared to normal liver tissue and refraction of the sound beam
- round nodule of homogenous fat attenuation (-20 to -70 HU)
- pure lipomas have no soft tissue component or enhancement
Round nodule with signal characteristics of macroscopic fat:
- T1: high signal
- T2: high signal
- fat-suppressed sequences: diffuse signal loss
- marginal India-ink artifact
- small lesions may appear to lose signal entirely from chemical shift artifact, due to limited spatial resolution
Additional hepatic lesions that may contain macroscopic fat include:
- adenoma - may have macro- or microscopic fat
- pseudolipoma of Glisson capsule
- teratoma (rare)
- hepatic adrenal rest tumors (HART) (rare)
- xanthomatous lesions of Langerhans cell histiocytosis (rare)
- metastases (extremely rare)
- the vast majority of metastases do not contain fat