Hepatic Metastases and Lymphoma

 Diffuse infiltration and low density on NECT


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


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

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

• Cystic metastases (< 20 HU)
image Fluid levels, debris, mural nodules

• Liver-specific MR contrast agents (e.g., gadoxetate)
image Metastases: Hypointense lesions made more apparent compared with bright enhancement of liver on delayed phase imaging

• CECT is usually best as “whole body” screening test
image Even better if combined as PET/CT

image Metastases and lymphoma are usually FDG-avid masses within liver

• Decision for thermal ablation or surgical resection
image May require most sensitive tests (gadoxetate-enhanced MR, PET/CT, or intraoperative US)




TOP DIFFERENTIAL DIAGNOSES




• Multifocal fatty infiltration (steatosis)

• Multiple benign masses

• Multifocal hepatocellular carcinoma or cholangiocarcinoma


DIAGNOSTIC CHECKLIST




• In absence of a known primary tumor or other metastases:
image Hepatic lesions that are “too small to characterize” rarely represent metastases

image Lesions that are lower than blood density on NECT rarely represent metastases

image
(Left) Axial CECT shows multiple spherical liver lesions image with a “target” appearance. This is the most typical appearance for liver metastases, especially from colon cancer. Also note the focally dilated bile ducts image due to compression by the metastases.


image
(Right) Color Doppler ultrasound in the same patient shows multiple spherical liver lesions with a “target” appearance image, some containing visible blood vessels image. This is the typical appearance of metastatic colorectal carcinoma.

image
(Left) Axial T1WI C+ MR in a patient with metastatic colon cancer shows multiple liver metastases with several typical features, including a continuous ring of enhancement image.


image
(Right) Axial T2WI FS MR in the same patient shows heterogeneous hyperintensity within the hepatic metastases image. Most metastases are heterogeneously hyperintense on T2WI and hypovascular and hypointense on T1WI.


TERMINOLOGY


Abbreviations




•  


Synonyms


 



Definitions




• Lymphoma: Neoplasm of lymphoid tissues

• Metastases: Malignant spread of neoplasm to hepatic parenchyma


IMAGING


General Features




• Best diagnostic clue
image Lymphoma: Lobulated, low-density, hypovascular masses

image Metastases: Multiple heterogeneous, spherical lesions scattered throughout liver

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

• Size
image Variable; few millimeters to > 10 centimeters

• Morphology
image Usually spherical

• Key concepts
image Hepatic lymphoma
– Primary (rare)

– Secondary (more common): Seen in > 50% of patients with Hodgkin disease (HD) or non-Hodgkin lymphoma (NHL)

– High-risk groups: Transplant recipients and AIDS patients

– Types of hepatic lymphoma: NHL > Hodgkin

image Liver metastases
– Most common malignant tumor of liver
image Compared to primary malignant tumors (18:1)

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

– Autopsy studies reveal 55% of oncology patients have liver metastases


CT Findings




• NECT
image Lymphoma
– Diffuse infiltration: Indistinguishable from normal liver or steatosis

image Metastases
– Isodense, hypodense, or hyperdense (melanin or calcification)

• CECT
image Lymphoma
– Diffuse infiltration and low density

– Multiple well-defined, homogeneous, low-density masses

image Hypovascular metastases
– Low-attenuation center with peripheral rim enhancement (e.g., epithelial metastases)

– Indicates vascularized viable tumor in periphery and hypovascular or necrotic center

– Rim enhancement may also be due to compressed normal parenchyma

image Hypervascular metastases
– Hyperdense in late arterial phase images

– May have internal necrosis without uniform hyperdense enhancement

– Hypo-/isodense on NECT and portal venous phase
image Often washout to become hypodense on delayed phase CECT

– Examples: endocrine (islet cell), carcinoid, thyroid and renal carcinomas, and pheochromocytoma

image Cystic metastases (< 20 HU)
– Fluid levels, debris, mural nodules


MR Findings




• T1WI
image Lymphoma and metastases: Hypointense lesions
– Melanoma metastases: Hyperintense due to melanin

• T2WI
image Lymphoma: Focal or diffusely hyperintense

image Metastases
– Moderate to high signal

– Light bulb sign: Very high signal intensity (e.g., cystic and neuroendocrine metastases)
image Mimic cysts or hemangiomas but usually with thick wall or fluid level

• T1WI C+
image Hypovascular metastases
– Same pattern of enhancement as CECT

– Low signal in center and peripheral rim enhancement

– Perilesional enhancement may be tumor vascularity or hepatic edema

image Hypervascular metastases
– Hyperintense enhancement on arterial phase

• Hepatobiliary contrast agents (e.g., gadoxetate [Eovist, Primovist])
image On delayed scans, normal liver is brightly enhanced

image Metastases are conspicuous as hypointense focal lesions

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


Ultrasonographic Findings




• Grayscale ultrasound
image Hepatic lymphoma
– Multiple well-defined, hypoechoic lesions

– Diffuse form: May detect innumerable subcentimeter hypoechoic foci
image Otherwise indistinguishable from normal or fatty liver

image Hypoechoic metastases
– Usually from hypovascular tumors

image Hyperechoic metastases
– GI tract malignancy

– Vascular metastases

image Bull’s-eye or “target” metastatic lesions
– Alternating layers of hyper- and hypoechoic tissue

– Solid mass with hypoechoic rim or halo

– Usually from aggressive primary tumors

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Nov 16, 2016 | Posted by in GASTROINTESTINAL IMAGING | Comments Off on Hepatic Metastases and Lymphoma

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