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Gastrointestinal Imaging |
1 Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10021 (L.H.S., E.J.G., S.M.C., M.C.E., D.M.P.)
2 Cornell University Medical College, New York, NY (L.H.S., E.J.G., D.M.P.).
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Abstract |
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 TOP Abstract IntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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MATERIALS AND METHODS: The authors reviewed the CT reports obtained in 2,978 patients with cancer during a 24-month period. Small hepatic lesions (lesions 1 cm or less in diameter or deemed too small to characterize by the interpreting radiologist) noted on the initial scan were assessed at follow-up CT. The number and type of any other intrahepatic lesion, the histologic type of the primary tumor, and the presence of extrahepatic metastatic disease were also recorded.
RESULTS: Small hepatic lesions were reported in 378 (12.7%) patients; 15 (4.0%) of these patients also reportedly had other larger hepatic lesions that were interpreted as metastases. Small hepatic lesions demonstrated interval growth in 44 (11.6%) patients and were therefore considered metastatic. Small hepatic lesions in 303 (80.2%) patients demonstrated no interval growth (mean follow-up, 25.6 months; range, 6–56 months) and were therefore presumed benign. Small hepatic lesions in 31 (8.2%) patients were stable at follow-up of less than 6 months and were considered indeterminate. Among the three most common tumors (lymphoma and colorectal and breast cancers), small hepatic lesions were metastatic in 4%, 14%, and 22%, respectively.
CONCLUSION: Although small hepatic lesions in patients with cancer more frequently are benign than malignant, these lesions represent metastases in 11.6% of patients.
Index terms: Liver, CT, 761.12112 • Liver, cysts, 761.3121 • Liver neoplasms, 761.31, 761.32, 761.33 • Liver neoplasms, CT, 761.12112 • Liver neoplasms, metastases, 761.33
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Introduction |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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The purpose of this study was to evaluate the prevalence and clinical importance of small hepatic lesions detected at CT in patients with various types of cancer.
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MATERIALS AND METHODS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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The histologic type of other larger hepatic lesions present (eg, hemangioma, cyst, focal nodular hyperplasia, metastasis, or indeterminate) was classified by the interpreting radiologist on the basis of characteristic CT appearances or characteristic findings on other imaging studies. Small hepatic lesions were considered benign if they were stable in size and appearance at follow-up imaging for at least 6 months. Small hepatic lesions were considered metastatic if they enlarged at any time (and did not have characteristic CT findings of hemangioma, cyst, or focal nodular hyperplasia). Small hepatic lesions with less than 6 months follow-up were considered indeterminate (unless they showed interval growth). Extrahepatic metastatic disease, when present, was recorded according to site, as follows: adrenal, bone, peritoneum, lung (seen at visualized lung bases), lymph node, or other.
CT scans were reviewed in selected cases when the reports of follow-up examinations with respect to small liver lesions were unclear. We did not review the images from patients in whom multiple liver metastases, but no small hepatic lesions, were found on their initial scans, even though it is likely that small hepatic lesions were present in some such cases. These patients were not included in the total number of patients in whom small hepatic lesions were reported.
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RESULTS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Thirty-one (8.2%) of the 378 patients had small hepatic lesions that were stable at follow-up of less than 6 months; such lesions were classified as indeterminate. To assess the potential effect these indeterminate small hepatic lesions had on the results, three analyses were performed. If all indeterminate small hepatic lesions were considered benign, then the overall prevalence of benign and malignant small hepatic lesions would be 88.4% and 11.6%, respectively. If all indeterminate small hepatic lesions were considered malignant, the overall prevalence of benign and malignant small hepatic lesions would be 80.2% and 19.8%, respectively. If half of the indeterminate small hepatic lesions were considered benign and half were considered malignant, the overall prevalence of benign and malignant small hepatic lesions would be 84.3% and 15.7%, respectively.
Patients in whom a small hepatic lesion was benign were less likely to have extrahepatic metastases than patients in whom a small hepatic lesion was metastatic (25.7% [78 of 303 patients] vs 36% [16 of 44 patients], respectively), but this difference was not statistically significant (P > .05, 
2). The most common site of extrahepatic metastasis in patients with small hepatic lesions of any cause was the lymph nodes; small hepatic lesions were benign in 43 (81%) of 53 patients with lymph node involvement and malignant in seven (13%) (Table 2). In the 23 patients with metastases to the lung bases, the small hepatic lesions were benign in 13 (57%) and malignant in seven (30%).
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2).
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DISCUSSION |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Small hepatic lesions often are due to a hepatobiliary fibrocystic continuum including simple cysts, benign bile duct lesions (biliary hamartomas and biliary microhamartomas), and polycystic syndromes (3,4). Biliary microhamartomas, also called Von Meyenburg complexes, consist of a dense fibrous stroma surrounding epithelial-lined irregular spaces that may contain bile (5). Von Meyenberg complexes are congenital lesions that can dilate and may result in liver cysts of adult polycystic disease as well as simple hepatic cysts (4). Hepatic insults such as ischemia or trauma may also play a role in the development of simple cysts. These lesions have a nonspecific appearance and manifest as single or multiple hypoattenuating foci on contrast material–enhanced CT scans (6). In routine autopsy series, the prevalence of hamartomas has been reported to be 0.69%–2.8% and has been thought to approximate the prevalence of radiologically demonstrated lesions (6). Others have reported a 27% prevalence of "bile duct tumors" (including microhamartomas and biliary adenomas) at targeted thin-section pathologic examination of the liver (2); this higher prevalence has been attributed to small lesions having been overlooked during routine, nontargeted, autopsies.
Small hepatic lesions were reported in 378 (12.7%) of 2,978 patients with cancer in our study. Most (80.2%) of these small lesions did not enlarge at follow-up imaging and were considered benign. This percentage is larger than that reported by Jones et al (1), likely because of the different criteria used to define small hepatic lesions. The prevalence of small hepatic lesions in our study ranged from 8% to 21% for those histologic tumor types with at least 10 patients with small hepatic lesions. This relatively narrow range suggests that there is a certain background prevalence of benign hepatic lesions—consistent with our findings that most small hepatic lesions are benign, even in patients with cancer. The prevalence of benign small hepatic lesions was approximately the same regardless of whether the lesions were single or associated with other liver lesions.
The large majority of CT examinations were performed with 10-mm collimation in the nonhelical mode. Spiral CT scanners were not available at our institution during the period in which initial scans were obtained. More liver lesions would be detected with thinner collimation and helical scanning (7); thus, the actual number of small hepatic lesions was underestimated. Of note, no radiologic examination can demonstrate all hepatic lesions present because lesions smaller than a few millimeters are below the resolution of current imaging techniques. The effect of nonhelical scanning would be to raise the size threshold at which small hepatic lesions would be demonstrated. There is no a priori reason, however, to suspect that smaller, undetected lesions are more likely to be malignant. Nevertheless, studies using helical CT and thinner collimation are needed to clarify this issue. Most of our patients underwent CT after monophasic injection of contrast material, which may also cause the actual number of small hepatic lesions to be underestimated. This study, however, was not designed to assess the sensitivity of various contrast-enhanced CT techniques for demonstrating small hepatic lesions. Instead, the purpose was to assess the importance of such lesions detected in daily clinical practice.
The actual number of small hepatic lesions in our patient population was certainly underreported when other, larger liver metastases were also present because our attending radiologists typically do not describe each of multiple liver lesions individually. The importance of additional, small hepatic lesions in the presence of other, larger hepatic metastases or extrahepatic metastases is generally minor unless the small lesions are new or hepatic resection is being contemplated; in such specific circumstances, our attending radiologists explicitly report such findings.
Lung cancer, a very common cancer, represents a relatively small proportion of tumors in this study because many of our patients with lung cancer underwent only an "extended" thoracic CT examination that included the adrenals and only part of the liver. Therefore, because of the unique distribution of primary tumors, our series may not represent a typical series of patients with metastatic disease. Of the three most common primary tumors in our study (lymphoma and colorectal and breast cancer), the prevalence of metastatic small hepatic lesions was greatest for breast cancer. Some of the other tumor types appear to have a higher prevalence of metastatic small hepatic lesions; however, this must be interpreted with caution because there were small numbers of patients with these other primary tumor types.
Many (16 of 44 [36%]) of the patients with small hepatic metastases also had associated extrahepatic metastases, which is not surprising given that the presence of extrahepatic metastases is suggestive of more widespread disease. Because we did not control for various stages of disease in different tumor types, our data cannot be used to predict whether a given small hepatic lesion is more or less likely to represent a metastasis in the presence of extrahepatic metastasis.
One limitation of our study is that it was a retrospective review of radiologic reports; it is likely that a more focused search for small hepatic lesions would have yielded additional cases. Actual CT scans were reviewed only in certain instances to clarify reported findings. Another limitation is that the benignity of a hepatic lesion was determined in most cases on the basis of its stability at follow-up CT, not by means of histologic confirmation. Our criterion of stability for at least 6 months and the relatively long follow-up available (mean, 25.6 months) were sufficiently long to support benignity. Liver metastases generally enlarge rapidly; for example, most patients with colorectal cancer die within 2 years of diagnosis (typically from liver failure), with a median survival time of 6 months (8). Doubling times of nearly all tumor types demonstrate substantial shortening once metastases arise (9). Potentially, a slow-growing metastasis would not be correctly categorized in our study. Our results were affected relatively little by the occurrence of indeterminate small hepatic lesions, as shown by rather similar results of three alternate analyses of those lesions.
In conclusion, we found that in a large population of patients with cancer, a hepatic lesion measuring 1 cm or smaller or deemed too small to characterize is most often benign (80.2%). Although small hepatic lesions in patients with cancer more frequently are benign than malignant, these lesions represent metastases in 11.6% of patients. This information may or may not obviate biopsy of a small hepatic lesion in a given patient with cancer but can be used to estimate the likelihood of metastasis and to determine the need for further evaluation of the lesion.
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Footnotes |
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From the 1997 RSNA scientific assembly.
Author contributions: Guarantors of integrity of entire study, L.H.S., E.J.G.; study concepts, L.H.S., E.J.G.; study design, L.H.S., D.M.P.; definition of intellectual content, L.H.S., D.M.P.; literature research, E.J.G., L.H.S.; clinical studies, E.J.G., S.M.C.; data acquisition, S.M.C., E.J.G.; data analysis, L.H.S., E.J.G., M.C.E.; statistical analysis, L.H.S., E.J.G., M.C.E.; manuscript preparation, E.J.G., L.H.S., D.M.P.; manuscript editing and review, L.H.S., E.J.G., S.M.C., M.C.E., D.M.P.
Received March 19, 1998;
revision requested May 22, 1998; revision received June 3, 1998;
accepted August 24, 1998.
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References |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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