Liver Masses Part 1
Review of the body radiology and nuclear medicine appearance of commonly tested liver lesions for ABR core exam review.
Study Guide/Show Notes:
Hepatocellular carcinoma (HCC) develops along a spectrum. Describe the spectrum of HCC development including some imaging manifestations.
HCC starts with regenerative nodules that progress to dysplastic nodules and then to HCC. Key imaging manifestations include that dysplastic nodules tend to be dark on T2 weighted images and HCC tends to be bright on T2 weighted images. Regenerative nodules may be bright or dark on T2 weighted images but typically do not enhance or washout differently than normal liver. Dysplastic nodules may have arterial enhancement but no washout. HCC demonstrates early arterial enhancement and delayed washout. Key imaging manifestations for HCC is a T2 bright mass vs masses with arterial enhancement and delayed washout, with co-existing findings of cirrhosis and portal hypertension.
What are some of the common risk factors for development of hepatocellular carcinoma?
Cirrhosis of any cause, acute hepatitis B with or without cirrhosis and chronic hepatitis B with cirrhosis, hepatitis C, hemochromatosis (HCC accounts for about 1/3 of deaths in hemochromatosis patients), glycogen storage disease, alpha-1 antitrypsin deficiency, other entities to include Budd Chiari syndrome.
True or false? most patients with HCC will have an elevated alpha fetal protein (AFP) level.
True, up to 95% of HCC patients will have elevated AFP levels.
What are imaging manifestations for the fibrolamellar HCC variant to look for on board exams?
Buzzword on board exams for fibrolamellar HCC is a central nonenhancing T2 dark scar on MRI. The central scar may be calcified on CT. Additionally, fibrolamellar HCC tends to develop in patients younger than 35 years without cirrhosis and with normal AFP levels. Fibrolamellar HCCs are aggressive so you may also be shown local nodal and distant metastatic disease.
If you see a hepatic mass with a central scar demonstrating delayed enhancement on MRI what is this typical for?
Focal nodular hyperplasia classically has a central scar that demonstrates delayed enhancement.
What are other imaging manifestations of focal nodular hyperplasia (FNH) on MRI?
FNH presents with a spoke wheel or cut grapefruit appearance on post-contrast imaging that is commonly isointense to liver (hence a “stealth lesion”) on pre-contrast T1 and T2 weighted images. With gadolinium on arterial enhanced images, you often see a cut grapefruit appearance due to enhancement in the mass surrounding a non-enhancing central scar with radiating bands. On delayed post-contrast images, the central scar will classically show delayed enhancement. Most common clinical history would be a mass in a middle-aged woman. FNH’s may regress with age. Note that FNH’s do not demonstrate washout of contrast as in HCC.
What nuclear medicine scan should you remember for FNH diagnosis on board exams?
On board exams I would remember that FNH can show uptake on a sulfur colloid liver scan. An FNH has normal hepatocytes around abnormally arranged ducts and Kupffer cells. As the lesion contains reticuloendothelial system cells you would expect that the RES will show sulfur colloid uptake. Other hepatic masses such as a hepatic adenoma, HCC, or metastasis would not be expected to show sulfur colloid uptake because these do not contain functioning Kupffer cells.
If a board exam question shows you a liver lesion and gives you a clinical history of a woman on oral contraceptives, what lesion should you think of first?
A question showing a liver lesion and providing a clinical history of oral contraceptive use should make you consider a hepatic adenoma as the most likely diagnosis. An alternative history also supporting a hepatic adenoma would be a male on anabolic steroids with a liver mass. Key is that hepatic adenomas are classically hormonally induced, thus may also be seen in obese individuals.
What is the imaging appearance of a hepatic adenoma?
Most commonly hepatic adenomas will present as a potentially large solitary mass in the right hepatic lobe (most common). If you see multiple hepatic adenomas, you can consider entities like glycogen storage disease (von Gierke’s disease). Hepatic adenomas classically contain internal fat (although male hepatic adenomas may not have fat) and/or hemorrhage. For board exams, if you see a lesion with sulfur colloid uptake think FNH instead of hepatic adenoma. On MRI, hepatic adenomas would classically show internal fat manifested by signal dropout on out of phase compared to in phase images, with early arterial enhancement and return to normal liver enhancement levels on delayed post-contrast images. Note that hepatic adenomas do not have washout like HCC. Washout=mass enhances less than normal liver on delayed post-contrast images—hepatic adenomas typically enhance like liver on delayed post-contrast images.
What is common clinical management of hepatic adenomas? What is a risk of hepatic adenoma that you should be aware of?
First step is to stop OCP/steroid use and then reimage. If a hepatic adenoma is < 5 cm in size on follow-up imaging, for board exams select that you recommend imaging surveillance as it may continue to regress. If a hepatic adenoma is >5 cm in size on follow-up this has a bleeding risk and a rare cancer HCC risk so for board exam purposes, you resect hepatic adenomas > 5 cm in size. Hepatic adenomas are thought to have poor internal connective tissue support, therefore larger lesions are prone to internal trauma and hemorrhage which may lead to acute pain and in some cases internal abdominal bleeding that can be serious.
What are similarities and differences of HCC and hepatic adenomas on imaging?
Similarities include hepatic lesions that may contain fat, and both can be well circumscribed. Differences include a typical homogenous post-contrast appearance of an adenoma and heterogeneous appearance of HCC. Both lesions demonstrate arterial enhancement but only HCCs classically show washout. If you have chronic liver disease it is HCC and not an adenoma on board exams.
What is the classic nuclear medicine appearance of hepatic adenoma versus focal nodular hyperplasia on a technetium sulfur colloid scan?
FNH will show uptake on Tc sulfur colloid as it has functioning Kupffer cells. Hepatic adenomas have poorly functioning or dysfunctional Kupffer cells so these would classically not show uptake and may even appear photopenic compared to liver on a Tc SC scan.
What is the imaging appearance of hepatic hemangiomas on CT or MRI?
On MRI hemangiomas are T2 bright masses. On CT hemangiomas are hypodense lesions. On both CT and MRI hemangiomas show peripheral nodular enhancement with progressive fill in of central enhancement on delayed enhancement images. Of note, because blood flow is slow and blood pools within these lesions, hepatic hemangiomas may enhance for about 30 minutes following contrast administration. Classic for hepatic hemangiomas is peripheral nodular interrupted enhancement with progressive filling in of contrast on more delayed post-contrast sequences. Really large hemangiomas can have venous pooling in venous lakes and central blood clots and can look heterogeneous, especially on T2 weighted images.
What is the ultrasound appearance of a hepatic hemangioma?
On ultrasound hemangiomas are well defined uniformly hyperechoic lesions. Surprisingly there is typically no visible doppler blood follow identified as the blood flow is often too slow to be identified.
Uptake with what nuclear medicine study is most typical for hepatic hemangiomas on board exams?
If you see a liver mass showing uptake on a tagged red blood cell nuclear medicine study, think hepatic hemangioma. I remember this as hemangioma has “hemangio” in the name which makes me think of blood as in a tagged RBC study. If you remember that hepatic hemangiomas have slow blood flow and blood pools in the lesion it makes perfect sense that tagged RBCs would also pool in the lesion and would therefore show uptake on nuclear medicine scintigraphy. The “hemangio” in the name is your clue that this would show up on a tagged RBC scan because the name is telling you about vascularity.
What is the “starry sky” appearance of the liver on ultrasound and what disease state does this suggest?
The starry sky appearance is a sign of hepatitis on ultrasound and shows echogenic fat around portal triads that stands out due to background liver edema.
Are benign liver masses more common or less common in a cirrhotic liver?
Benign liver masses tend to go away or not develop and are much less common in a cirrhotic liver. Therefore, treat any liver lesion in a cirrhotic patient with some suspicion.
Carcinoid and HCC are both arterial enhancing masses—how do you tell the difference between these on board exams?
If you see chronic liver disease it is HCC on board exams. In general, chronic liver disease is highly inhospitable to both benign masses and metastatic disease so it is less likely to get liver metastases in the setting of chronic liver disease. So, if you see a Hypervascular mass in chronic liver disease it is HCC versus a Hypervascular metastasis such as carcinoid. Other tips include seeing the carcinoid tumor to suggest that the liver lesion is a metastasis.
