Hepatocellular carcinoma (HCC, also called malignant hepatoma) is the most common type of liver cancer. Most cases of HCC are secondary to either a viral hepatitide infection (hepatitis B or C) or cirrhosis (alcoholism being the most common cause of hepatic cirrhosis).
Compared to other cancers, HCC is quite a rare tumor in the United States. In countries where hepatitis is not endemic, most malignant cancers in the liver are not primary HCC but metastasis (spread) of cancer from elsewhere in the body, e.g., the colon. Treatment options of HCC and prognosis are dependent on many factors but especially on tumor size and staging.
Tumor grade is also important. High-grade tumors will have a poor prognosis, while low-grade tumors may go unnoticed for many years, as is the case in many other organs, such as the breast, where a ductal carcinoma in situ (or a lobular carcinoma in situ) may be present without any clinical signs and without correlate on routine imaging tests, although in some occasions it may be detected on more specialized imaging studies like MR mammography.
On CT, HCC can have three distinct patterns of growth:
A single large tumor
Poorly defined tumor with an infiltrative growth pattern
A biopsy is not needed to confirm the diagnosis of HCC if certain imaging criteria are met.
The key characteristics on CT are hypervascularity in the arterial phase scans, washout or de-enhancement in the portal and delayed phase studies, a pseudocapsule and a mosaic pattern. Both calcifications and intralesional fat may be appreciated.
An alternative to a CT imaging study would be the MRI. More important MRI are just beginning to be used in tumor detection and fewer radiologists are skilled at finding tumors with MRI studies when it is used as a screening device. Mostly the radiologists are using MRIs to do a secondary study to look at an area where a tumor has already been detected. MRI’s also use contrast agents. One of the best for showing details of liver tumors is very new: iron oxide nano-particles appears to give better results. The latter are absorbed by normal liver tissue, but not tumors or scar tissue.
Axial CT views of arterial-phase (A) and venous-phase (B) scans of patient with unifocal HCC.
MRI Poorly differentiated hepatocellular carcinoma:
Axial SPIO-enhanced 2D T2*-weighted (TE = 6.6 msec) spoiled GRE image obtained at 1.5 T shows a poorly defined high-signal-intensity mass (arrows) at the junction of liver segments V and VIII, abutting the liver capsule and causing it to retract.
Axial gadolinium-enhanced 3D fat-saturated T1-weighted spoiled GRE images obtained in hepatic arterial and equilibrium phases show heterogeneous enhancement of the mass, with rimlike (white arrowheads) and geographic (black arrowheads) high-signal-intensity areas and a low-signal-intensity center (arrow), a finding suggestive of ischemia or necrosis.