Diagnostic Ultrasound - Abdomen and Pelvis

Hepatic Adenoma
TERMINOLOGY
Synonyms
• Hepatocellular adenoma (HCA) or liver cell adenoma
Definitions
• Benign tumor that arises from hepatocytes arranged in
cords that occasionally form bile
IMAGING
General Features
• Best diagnostic clue
○ Heterogeneous, hypervascular mass with hemorrhage in
a young woman, often with contraceptive use
• Location
○ Usually subcapsular right hepatic lobe (75%)
○ Intraparenchymal or pedunculated (10%)
• Size
○ Varies 1-30 cm, average 5-10 cm
• Key concepts
○ Rare benign neoplasm
○ 2nd most frequent hepatic tumor in young women after
focal nodular hyperplasia (FNH)
○ Associated with oral contraceptive use
○ Usually single in 70-80% of cases (adenoma); rarely
multiple (adenomatosis)
Ultrasonographic Findings
• Grayscale ultrasound
○ Well-defined borders
○ Round or mildly lobulated contour
○ 20-40% hypoechoic; 30% hyperechoic; 30% isoechoic
○ Complex hyper- and hypoechoic heterogeneous mass
with anechoic/hypoechoic areas
– Due to fat, hemorrhage, necrosis, and calcification
○ Hypoechoic halo of compressed liver tissue
○ Intratumoral or intraperitoneal hemorrhage from acute
rupture (potential complication)
• Color Doppler
○ Hypervascular tumor, supplied by hepatic artery
○ Large peripheral arteries and veins
○ Intratumoral veins present
– Absent in FNH
– Useful discriminating feature for HCA
CT Findings
• NECT
○ Isodense to hypodense (due to lipid)
○ Hemorrhage: Intratumoral, parenchymal, or subcapsular
• CECT
○ Arterial phase
– Heterogeneous, hyperenhancing
○ Portal venous phase
– Less heterogeneous
– Hyper-/iso-/hypodense to liver
○ Delayed phase (5-10 minutes)
– Enhancement does not persist (due to arteriovenous
shunting)
– Pseudocapsule: Hyperattenuated to liver and
adenoma
MR Findings
• T2WI
○ Mass: Heterogeneous signal intensity
– Increased signal intensity (old hemorrhage/necrosis)
– Decreased signal intensity (fat, recent hemorrhage)
○ Rim (fibrous pseudocapsule): Hypointense
• T1WI C+
○ Gadolinium arterial phase
– Mass: Heterogeneous early arterial enhancement
○ Delayed phase
– Mass: Becomes isointense to liver
– Pseudocapsule: Hyperintense to liver and adenoma
○ Gadoxetate-enhanced MR (liver-specific contrast agent)
– Mass: Hypointense on T1 hepatobiliary phase
• GRE in-/out-of-phase
○ Loss of signal on out-of-phase imaging due to
intralesional lipid
Angiographic Findings
• Conventional
○ Hypervascular mass with centripetal flow
○ Enlarged hepatic artery with feeders at tumor periphery
(50%)
○ Hypovascular; avascular regions due to hemorrhage,
necrosis
Nuclear Medicine Findings
• Technetium sulfur colloid
○ Usually "cold" (photopenic): 80%
○ Uncommonly "warm": 20%
– Due to uptake in sparse Kupffer cells
Imaging Recommendations
• Best imaging tool
○ Ultrasound is good for lesion detection, guiding biopsy,
and monitoring size
• T2WI; T1WI with dynamic enhanced multiphasic; GRE inand
opposed-phase images
• Liver-specific MR contrast agents have high accuracy for
differentiating HCA from other lesions
DIFFERENTIAL DIAGNOSIS
Hemangioma
• Hyperechoic mass ± posterior acoustic enhancement
• Large lesions may be heterogeneous
Focal Nodular Hyperplasia (FNH)
• No malignant degeneration or hemorrhage
• Central scar may be present
• When small (≤ 3 cm), FNH without scar may be
indistinguishable from adenoma
Hepatocellular Carcinoma (HCC)
• May be difficult to distinguish from adenoma on imaging
and histology
• Background cirrhosis usually present
• Biliary, vascular, nodal invasion, and metastases establish
that lesion is malignant
Fibrolamellar Carcinoma
• Heterogeneous, large, lobulated mass with scar and septa
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Diagnoses: Liver
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