Hepatocellular carcinoma (HCC) most commonly appears in a patient with chronic viral hepatitis (hepatitis B or hepatitis C, 20%) or with cirrhosis (about 80%). These patients commonly undergo surveillance with ultrasound due to the cost-effectiveness.
In patients with a higher suspicion of HCC (such as rising alpha-fetoprotein and des-gamma carboxyprothrombin levels), the best method of diagnosis involves a CT scan of the abdomen using intravenous contrast agent and three-phase scanning (before contrast administration, immediately after contrast administration, and again after a delay) to increase the ability of the radiologist to detect small or subtle tumors. It is important to optimize the parameters of the CT examination, because the underlying liver disease that most HCC patients have can make the findings more difficult to appreciate.
On CT, HCC can have three distinct patterns of growth:
- A single large tumor
- Multiple tumors
- 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.
CT scans use contrast agents, which are typically iodine or barium based. Some patients are allergic to one or both of these contrast agents, most often iodine. Usually the allergic reaction is manageable and not life threatening.
An alternative to a CT imaging study would be the MRI. MRI's are more expensive and not as available because fewer facilities have MRI machines. 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.
In a review article of the screening, diagnosis and treatment of hepatocellular carcinoma, 4 articles were selected for comparing the accuracy of CT and MRI in diagnosing this malignancy. Radiographic diagnosis was verified against post-transplantation biopsy as the gold standard. With the exception of one instance of specificity, it was discovered that MRI was more sensitive and specific than CT in all four studies.
Pathology
Macroscopically, liver cancer appears as a nodular or infiltrative tumor. The nodular type may be solitary (large mass) or multiple (when developed as a complication of cirrhosis). Tumor nodules are round to oval, grey or green (if the tumor produces bile), well circumscribed but not encapsulated. The diffuse type is poorly circumscribed and infiltrates the portal veins, or the hepatic veins (rarely).
Microscopically, there are four architectural and cytological types (patterns) of hepatocellular carcinoma: fibrolamellar, pseudoglandular (adenoid), pleomorphic (giant cell) and clear cell. In well differentiated forms, tumor cells resemble hepatocytes, form trabeculae, cords and nests, and may contain bile pigment in cytoplasm. In poorly differentiated forms, malignant epithelial cells are discohesive, pleomorphic, anaplastic, giant. The tumor has a scant stroma and central necrosis because of the poor vascularization.
Staging
Important features that guide treatment include: -
- size
- spread (stage)
- involvement of liver vessels
- presence of a tumor capsule
- presence of extrahepatic metastases
- presence of daughter nodules
- vascularity of the tumor
MRI is the best imaging method to detect the presence of a tumor capsule.
Prognosis
The usual outcome is poor, because only 10 - 20% of hepatocellular carcinomas can be removed completely using surgery.
If the cancer cannot be completely removed, the disease is usually fatal within 3 - 6 months. However, survival can vary, and occasionally people will survive much longer than 6 months.the prognosis for metastatic or unresectable hepatocellular carcinoma has recently improved do to the approval of nexavar for advanced hepatocellular carcinoma.
Further Reading
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"Hepatocellular carcinoma"
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