ACR Appropriateness Criteria®
Clinical Condition: Liver Lesion Characterization
Variant 1: Typical benign on initial imaging, no history of malignancy.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| No imaging/procedure at this time. Recommend follow-up imaging at an appropriate time. |
8 |
If classic hemangioma, simple cyst, or FNH, no further imaging needed. |
| US, abdomen |
5 |
Particularly useful if follow-up is to be performed. |
| MRI, abdomen, with contrast |
4 |
|
| CT, abdomen, helical with late arterial and portal venous phase imaging |
4 |
|
| MRI, abdomen, without contrast |
4 |
|
| NUC, Tc-99m sulfur colloid or Tc-99m RBC |
4 |
|
| INV, angiography |
2 |
|
| INV, percutaneous biopsy |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 2: Typical benign on initial imaging, known history of extrahepatic malignancy.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| No imaging/procedure at this time. Recommend follow-up imaging at an appropriate time. |
8 |
If classic hemangioma, simple cyst, or FNH, no further imaging needed. |
| US, abdomen |
5 |
|
| CT, abdomen, helical with late arterial and portal venous phase imaging |
5 |
|
| MRI, abdomen, with contrast |
5 |
|
| MRI, abdomen, without contrast |
4 |
|
| NUC, Tc-99m sulfur colloid or Tc-99m RBC |
2 |
|
| INV, angiography |
2 |
|
| INV, percutaneous biopsy |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 3: Typical malignant hepatic mass on initial imaging.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| No imaging/procedure at this time. Recommend follow-up imaging at an appropriate time. |
7 |
Require risk assessment and biochemical analysis for HCC. |
| INV, percutaneous biopsy |
7 |
Require risk assessment and biochemical analysis for HCC. |
| CT, abdomen, helical with late arterial and portal venous phase imaging |
6 |
|
| MRI, abdomen, with contrast |
6 |
|
| MRI, abdomen, without contrast |
4 |
|
| US, abdomen |
4 |
|
| NUC, Tc-99m sulfur colloid or Tc-99m RBC |
2 |
|
| INV, angiography |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 4: Indeterminate on initial imaging, >1 cm, no suspicion or evidence of extrahepatic malignancy or liver disease.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| CT, abdomen, helical with late arterial and portal venous phase imaging |
8 |
Either MRI or CT, depending on availability and institutional preference. |
| MRI, abdomen, with contrast |
8 |
Either MRI or CT, depending on availability and institutional preference. |
| INV, percutaneous biopsy |
5 |
Require risk assessment and biochemical analysis for HCC. |
| MRI, abdomen, without contrast |
5 |
|
| US, abdomen |
5 |
|
| NUC, Tc-99m sulfur colloid or Tc-99m RBC |
3 |
May be of use if classic hemangioma or focal nodular hyperplasia lesion suspected. |
| INV, angiography |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 5: Indeterminate solitary mass on initial imaging, >1 cm, known history of extrahepatic malignancy.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| INV, percutaneous biopsy |
8 |
|
| CT, abdomen, helical with late arterial and portal venous phase imaging |
7 |
|
| MRI, abdomen, with contrast |
7 |
|
| CT/PET |
7 |
Confirmation of metastatic disease if findings would influence patient management. |
| MRI, abdomen, without contrast |
6 |
|
| US, abdomen |
5 |
|
| NUC, Tc-99m sulfur colloid or Tc-99m RBC |
3 |
|
| INV, angiography |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 6: Indeterminate mass on initial imaging, >1 cm, known or suspected liver disease associated with a high risk of hepatocellular carcinoma (chronic hepatitis, cirrhosis, hemochromatosis, etc.).
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| MRI, abdomen, with contrast |
8 |
Either MRI or CT, depending on availability and institutional preference. |
| CT, abdomen, helical with late arterial and portal venous phase imaging |
8 |
Either MRI or CT, depending on availability and institutional preference. |
| INV, percutaneous biopsy |
6 |
Depends on results of AFP |
| MRI, abdomen, without contrast |
5 |
|
| US, abdomen |
3 |
|
| NUC, Tc-99m sulfur colloid or Tc-99m RBC |
2 |
|
| INV, angiography |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 7: Small lesion on initial imaging, <1 cm.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| No imaging/procedure at this time. Recommend follow-up imaging at an appropriate time. |
8 |
|
| US, abdomen |
7 |
|
| CT, abdomen, helical with late arterial and portal venous phase imaging |
5 |
|
| MRI, abdomen, with contrast |
5 |
|
| MRI, abdomen, without contrast |
4 |
|
| NUC, Tc-99m sulfur colloid or Tc-99m RBC |
2 |
|
| INV, angiography |
2 |
|
| INV, percutaneous biopsy |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Due to the high prevalence of benign focal hepatic lesions in adults, liver lesion characterization is an important objective of diagnostic imaging. For example, "incidental" liver masses discovered in healthy adults as well as liver lesions detected during staging of a known malignancy often need to be characterized.
Common benign liver masses include cysts and hemangiomas, and common malignant tumors are metastases and HCC. Less common liver tumors include FNH, liver cell adenoma (LCA), fibrolamellar HCC, intrahepatic cholangiocarcinoma, biliary cystadenoma and cystadenocarcinoma, lymphoma, hemangioendothelioma, hepatoblastoma in children, and a variety of sarcomas. On occasion, nontumorous masses seen as focal fat sparing, abscess, or hematoma may mimic liver tumors. Patients with cirrhosis are a special group in whom certain benign (regenerating nodules), premalignant (dysplastic nodules), malignant (HCC), and nontumorous (confluent hepatic fibrosis) masses are more prevalent.
The various variants in this document assume that state-of-the-art imaging studies have already been performed and that no prior imaging studies are available for comparison. For ultrasonography, this includes high-resolution sonography with color flow evaluation; for CT, it includes mechanically injected, intravenous (IV) contrast media–enhanced, dynamic helical, or multidetector helical CT; and, for MRI, it includes T1- and T2-weighted imaging plus multiphase dynamic scanning with gadolinium chelate enhancement.
Variant Development
"Liver lesion characterization" is undertaken for hepatic masses seen by US, CT, or MRI. For the variant analysis, one can consider the following clinical situations:
Typical Benign: Incidental liver lesion whose US, CT, or MRI imaging appearance is highly suggestive of a benign mass (cyst, hemangioma, focal fat, or FNH). This may occur in a patient with or without a known history of malignancy.
Typical Malignant: Incidental liver lesion whose US, CT, or MRI imaging appearance is highly suggestive of a malignant mass (HCC, cholangiocarcinoma, or metastases) in a patient who may or may not have a known malignancy.
Indeterminate: Larger than 1 cm incidental liver lesion whose US, CT, or MRI imaging appearance is indeterminate. This may occur in a patient with a background of normal liver, chronic liver disease, or known extrahepatic primary malignancy.
Small: Subcentimeter liver lesions whose US, CT, or MRI imaging appearance is indeterminate, regardless of clinical history.
Diagnostic Tests
For characterization of a liver lesion discovered by US, CT, or MRI, the following diagnostic studies may be considered:
- Dynamic contrast-enhanced CT (helical, or multidetector helical)
- MRI (including contrast enhancement with gadolinium chelates, iron oxide, and mangafodipir)
- Sonography
- CT/PET
- Nuclear scintigraphy (Tc-99m sulfur colloid or Tc-99m RBC)
- Angiography
- Percutaneous biopsy
- Follow-up imaging using the same test as the original study at an appropriate time interval
Research in US contrast agents performed outside the United States has demonstrated high accuracy in characterizing liver lesions. These agents have not been approved for hepatic imaging in the United States.
When considering possible studies for liver lesion characterization, it is assumed that a logical sequence will be followed. For example, if MRI and biopsy are considered appropriate tests, it is assumed that the biopsy will be done only if the MRI is nondiagnostic. In this case, both studies should be considered "indicated."
Recommendations
Typical Benign Mass: No History of Malignancy. Liver masses with typical imaging features of simple cyst, hemangioma, or FNH in patients who are not known to have, or are not suspected of having, a malignancy may be classified as benign. Focal fat or focal spared areas in fatty livers can generally be diagnosed when typical features are seen on sonography, noncontrast CT, and most reliably, MRI using in-phase and out-of-phase scanning.
Typical Benign Mass: Known History of Malignancy. Liver masses with typical imaging features of simple cyst, hemangioma, or FNH in patients who are known to have a malignancy may be considered benign. However, if there is any doubt that the mass is benign, follow-up imaging (using the same test with which the lesion was initially detected) should be performed to make sure there is no change in the lesion appearance. Alternatively, MRI could be performed to help enable a definitive diagnosis. Presence of focal fat can be ascertained with MRI using in-phase and out-of-phase scanning.
Typical Malignant Mass: Lesions with typical sonographic, CT, or MRI features of a malignant mass do not require additional imaging but confirmation with serum tumor markers (HCC) or percutaneous biopsy may be appropriate.
Indeterminate Mass: Normal Liver. For indeterminate masses, additional imaging may be required for tissue characterization. In these patients, follow-up imaging is not a practical option due to the need to initiate appropriate treatment. If the initial indeterminate imaging test is sonography or CT, then MRI may be considered for liver lesion characterization. MRI would be preferred in pediatric and young adult patients due to lack of ionizing radiation. Nuclear scintigraphy is an option in patients with suspected FNH (technetium-labeled sulphur colloid) or possible neuroendocrine liver metastasis (somatostatin receptor scintigraphy).
Indeterminate Mass: Suspect Metastatic Disease. For indeterminate masses, additional imaging may be required for tissue characterization. In these patients, follow-up imaging is not a practical option due to the need to initiate appropriate treatment. In suspect metastatic disease, dynamic multidetector helical CT and contrast-enhanced multiphase MRI (gadolinium enhanced) may be considered. CT/PET imaging is strongly suggested if the suspect metastasis will likely be fluorodeoxyglucose (FDG) avid (e.g., melanoma, colon and esophageal cancer, breast cancer, sarcoma) and a diagnosis of liver metastasis will influence patient management. Nuclear scintigraphy is an option in patients with possible neuroendocrine liver metastasis (somatostatin receptor scintigraphy).
Indeterminate Mass: Cirrhotic Liver. Characterization of liver lesions in a cirrhotic liver is best performed with either contrast-enhanced MRI (gadolinium) or dynamic multidetector helical CT, but that characterization is imperfect. Characterization is more definitive for lesions larger than 2 cm in diameter. Although MRI may sometimes differentiate among regenerating nodules, dysplastic nodules, and HCC, MRI (like CT and US) is best used as follow up lesions to determine change in appearance. Percutaneous biopsy is often needed to make a final diagnosis.
Additional MRI contrast agents including mangafodipir and ferumoxide may be of value distinguishing benign and malignant primary hepatocellular tumor and detecting metastatic disease. However, experience with the use of these agents is mainly limited to Phase III clinical trials, and these agents are not widely available for clinical use.
For indeterminate liver lesions in all the categories considered above, a biopsy should be considered if the findings from the additional imaging tests are inconclusive.
Subcentimeter Lesion: These lesions are difficult to characterize. In patients with extrahepatic primary malignancy, these small lesions are best evaluated with follow-up imaging because most are benign.
Abbreviations
- AFP, alpha-fetoprotein
- CT, computed tomography
- FNH, focal nodular hyperplasia
- HCC, hepatocellular carcinoma
- INV, invasive
- MRI, magnetic resonance imaging
- NUC, nuclear medicine
- PET, positron-emission tomography
- RBC, red blood cell
- Tc-99m, Technetium 99 metastable
- US, ultrasound
