Diagnostic Ultrasound - Abdomen and Pelvis

Hepatic Metastases
TERMINOLOGY
Definitions
• Malignant spread of neoplasm to hepatic parenchyma
IMAGING
General Features
• Best diagnostic clue
○ Multiple lesions scattered throughout liver in random
distribution
• Location
○ Both lobes of liver
• Size
○ Variable from few mm to > 10 cm
• Key concepts
○ Most common malignant tumor of liver
○ Liver is 2nd only to regional lymph nodes as site of
metastatic disease
○ Autopsy studies reveal up to 55% of oncology patients
have liver metastases
Ultrasonographic Findings
• Grayscale ultrasound
○ Round or oval, with smooth or irregular borders
○ Causes architectural distortion if large or numerous
○ Hypoechoic metastases
– Usually from hypovascular tumors
○ Hyperechoic metastases
– Vascular metastases; from neuroendocrine tumors
(classically carcinoid), choriocarcinoma, renal cell
carcinoma, melanoma
○ "Bull's-eye" or "target" metastatic lesions
– Alternating layers of hyper- & hypoechoic tissue
– Solid mass with hypoechoic rim or halo
– Usually from aggressive primary tumors
– Classic example: Bronchogenic carcinoma
○ Cystic/necrotic metastases
– May demonstrate posterior enhancement
– Mural nodules, thick walls, fluid-fluid levels, internal
septa/debris distinguish them from simple cysts
– Necrotic center may be lined with irregular walls and
contain debris
– Cystic primaries: Cystadenocarcinoma of
pancreas/ovary; colon
– Necrosis/treated metastases: Sarcoma; squamous cell
carcinoma
○ Calcified metastases
– Markedly echogenic interface with acoustic
shadowing or diffuse small echogenic foci
– Mucinous primaries: Colon, ovary
– Calcific/ossific primaries: Osteosarcoma,
chondrosarcoma, neuroblastoma, malignant teratoma
– Treated metastases
○ Infiltrative/diffuse metastases
– Lung or breast primary
– Refractive shadows often emanate from infiltrative
tumor margins
– May simulate cirrhosis
– May distort or efface portal or hepatic veins
• Color Doppler
○ Follows vascularity of primary tumor
○ Contrast-enhanced US increases detectability of hepatic
metastases
– Vascularity in tumor bed
– Kupffer phase defect after microbubble
enhancement
CT Findings
• NECT
○ Calcified: Mucinous adenocarcinoma (colon), treated
metastases (breast), malignant teratoma
○ Cystic metastases (less than 20 HU)
– Fluid levels, debris, mural nodules
– Thickened walls or septations may be seen
– Usually cystadenocarcinoma or sarcoma (pancreatic,
GI, or ovarian primaries)
• CECT
○ Hypovascular metastases
– Low-attenuation center with peripheral rim
enhancement (e.g., epithelial metastases)
– Indicates vascularized viable tumor in periphery &
hypovascular or necrotic center
– Rim enhancement may also be due to compressed
normal parenchyma
○ Hypervascular metastases
– Hyperdense in late arterial phase images
– May have internal necrosis without uniform
hyperdense enhancement
– Hypo- or isodense on NECT & portal venous phase;
often washout becomes hypodense on delayed phase
– e.g., neuroendocrine tumor, thyroid, breast, renal cell
carcinomas, and pheochromocytoma
MR Findings
• T1WI
○ Melanoma metastasis: Hyperintense due to melanin
• T2WI
○ Moderate to high signal
○ "Light bulb" sign: Seen with cystic and neuroendocrine
tumor metastases
– Mimic cysts or hemangiomas, but usually with thick
wall or fluid level
• T1WI C+
○ Hypovascular metastases
– Same pattern of enhancement as CECT
– Low signal in center and peripheral rim-enhancement
– Perilesional enhancement may be tumor vascularity or
hepatic parenchymal edema
○ Hypervascular metastases
– Hyperintense enhancement on arterial phase
○ Hepatobiliary contrast agent (gadoxetic acid):
Hepatobiliary phase (20 min)
– Metastases are conspicuous as hypointense focal
lesions, whereas normal liver parenchyma retains
contrast
– Sensitive imaging modality for determining presence
and number of metastases (especially for
neuroendocrine metastases to liver) but not specific
Imaging Recommendations
• Best imaging tool
○ CECT for tumor staging
http://radiologyebook.com/
Diagnoses: Liver
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