Hepatic Metastases and Lymphoma

Multiphasic CT or MR are 1st-line tests

Accuracy: Helical CT (~ 80%), MR and PET (~ 90%)

Hepatic lymphoma

• Diffuse low density on CT may mimic steatosis

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    Easily distinguished from steatosis on MR

• Multiple well-defined, homogeneous, low-density (CECT) or high-intensity (T2WI) masses

Liver metastases

• Hypovascular metastases: Low-density center with peripheral rim or target-like enhancement

• Hypervascular metastases: Hyperdense (intense) on arterial-phase CECT or CEMR

Cystic metastases (< 20 HU)

• Fluid levels, debris, mural nodules

• Very bright (like cysts) on T2WI MR (but more complex)

Liver-specific MR contrast agents (e.g., gadoxetate)

• Metastases: Hypointense lesions become more apparent compared with bright enhancement of liver on delayed-phase imaging

CECT is usually best as whole-body screening test

• Even better if combined as PET/CT

• Metastases and lymphoma are usually FDG-avid masses

Decision for thermal ablation or surgical resection

• May require most sensitive tests (gadoxetate-enhanced MR, PET/CT, or intraoperative US)

US : Hypoechoic metastases; usually from hypovascular tumors

• Hyperechoic metastases: From GI or hypervascular primaries

• Cystic metastases: Complex walls and contents

Multiphasic (arterial- and venous-phase) CT

• Known or suspected hypervascular (e.g., endocrine) primary tumor

Lymphoma: Neoplasm of lymphoid tissues

Metastases: Malignant spread of neoplasm to hepatic parenchyma

Best diagnostic clue

• Lymphoma: Lobulated, low-density, hypovascular masses

• Metastases: Multiple hypo-/hyperdense lesions scattered throughout liver in random distribution

Location

• Lymphoma (HD & NHL) favors periportal areas due to high content of lymphatic tissue

Size

• Variable; few millimeters to > 10 centimeters

Morphology

• Usually spherical

Key concepts

• Hepatic lymphoma: Non-Hodgkin lymphoma (NHL) > Hodgkin lymphoma

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    Primary (rare); secondary in up to 50% of patients with NHL

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    High-risk groups: Transplant recipients and AIDS patients

• Liver metastases

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    Most common malignant tumor of liver

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      Compared to primary malignant tumors (18:1)

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    Liver is 2nd only to regional lymph nodes as site of metastatic disease

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    Autopsy studies reveal 55% of oncology patients have liver metastases

CECT

• Lymphoma

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    Diffuse infiltration and low density

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    Multiple well-defined, homogeneous, low-density masses

• Hypovascular metastases (most common type)

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    Low-attenuation center with peripheral rim enhancement

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    Indicates vascularized viable tumor in periphery and hypovascular or necrotic center

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    Rim enhancement may also be due to compressed normal parenchyma

• Hypervascular metastases (usually from endocrine primary tumor)

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    Hyperdense in late arterial-phase images

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    May have internal necrosis without uniform hyperdense enhancement

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    Hypo-/isodense on NECT and portal venous phase

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      Often washout to become hypodense on delayed-phase CECT

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    Examples: Islet cell, carcinoid, thyroid and renal carcinomas, and pheochromocytoma

• Cystic metastases (< 20 HU)

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    Fluid levels, debris, mural nodules

T1WI

• Lymphoma and metastases: Hypointense lesions

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    Melanoma metastases: Hyperintense due to melanin

T2WI

• Lymphoma: Focal or diffusely hyperintense

• Metastases

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    Moderate to high signal relative to background liver

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    Very high signal intensity (e.g., cystic and neuroendocrine metastases)

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      Mimic cysts or hemangiomas but usually with thick wall or fluid level

T1WI C+

• Hypovascular metastases

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    Same pattern of enhancement as CECT

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    Low signal in center and peripheral rim enhancement

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    Perilesional enhancement may be tumor vascularity or hepatic edema

• Hypervascular metastases

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    Hyperintense enhancement on arterial phase

Hepatobiliary contrast agents [e.g., gadoxetate (Eovist, Primovist)]

• On delayed scans, normal liver is brightly enhanced

• Metastases are conspicuous as hypointense focal lesions

• Most sensitive, but not specific, imaging test for determining presence and number of metastases

Grayscale ultrasound

• Hepatic lymphoma

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    Multiple well-defined, hypoechoic lesions

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    Diffuse form: May detect innumerable subcentimeter hypoechoic foci

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      Otherwise indistinguishable from normal or fatty liver

• Metastases: Heterogeneously echoic masses

• Bull's-eye or target metastatic lesions

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    Alternating layers of hyper- and hypoechoic tissue

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    Solid mass with hypoechoic rim or halo

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    Usually from aggressive primary tumors

• Cystic metastases

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    Almost all show complex walls and contents

• Calcified metastases

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    Markedly echogenic with acoustic shadowing

Intraoperative US: Reference standard for hepatic tumors of all kinds