Size May Predict Whether Lesions Benign or Malignant

The objective of a recent study was to determine if hepatic masses demonstrating homogeneous arterial phase enhancement that subsequently fade to isodensity are benign in noncirrhotic patients.

The study has concluded that hepatic lesions measuring >=22 mm that demonstrate homogeneous hyper enhancement on arterial phase imaging and subsequently fade to isoattenuation are benign in patients without cirrhosis.

Methodology
This retrospective analysis was comprised of 55 patients without cirrhosis who had 227 hepatic masses measuring >=5 mm demonstrating homogeneous arterial phase hyper enhancement that subsequently faded to isoattenuation. Inclusion criteria for the masses were round, oval, or lobulated shape; size >=5 mm; homogeneous on all imaging phases; and hyper enhancement on the hepatic arterial phase with fading to isoattenuation on portal venous and delayed phases relative to the hepatic parenchyma.

Multidetector CT examinations were performed during the hepatic arterial phase beginning 30 to 35 seconds, and portal venous phase at 65 to 70 seconds, following contrast injection. Delayed images at three to five minutes following injection were obtained only in select cases, when deemed necessary.

Results of the Study
There were 107 malignant and 120 benign transient homogeneously enhancing hepatic masses. None of the malignant masses were primary liver neoplasm. One of the malignant masses was diagnosed at liver resection, and the remaining 106 malignant lesions were diagnosed on the basis of interval growth in patients with a histologically confirmed extrahepatic primary neoplasm. Extrahepatic primary sites included breast, gastrointestinal tract adenocarcinoma, melanoma, neuroendocrine, renal cell carcinoma and sarcoma.

Of the 120 benign lesions, 112 remained stable in size over a 24-month period. Five of the 120 benign lesions were confirmed by histology; 2 were focal nodular hyperplasia and 3 were hepatic adenomas. The remaining 3 of the 120 benign masses had remained clinically stable and displayed imaging features of focal nodular hyperplasia on contrast enhanced sonography. All of the lesions measuring >=22 mm were benign. Lesions measuring <=21.5 mm were malignant in 54% and benign in 46% of the masses.

Conclusions
Therefore, hepatic lesions measuring >=22 mm that demonstrate homogeneous hyper enhancement on arterial phase imaging and subsequently fade to isoattenuation had 100% positive predictive value for benignity.

Meanwhile, a lesion measuring <21 mm had an equal probability of being benign or malignant.

Reviewer’s Comments
These results provide a logical approach to the commonly encountered incidental hyper- enhancing hepatic mass found on imaging. These lesions are particularly troublesome in patients without cirrhosis, and the clinical significance of these is commonly overestimated.

This study provides a few useful criteria to help stratify these lesions into benign or malignant categories. Consequently, this would not only provide for a more effective management algorithm, but would also decrease patient anxiety when benign lesions are encountered. One of the limitations reported in this study is probable over representation of malignant lesions given the patient population of this cancer center.

Author: John C. Sabatino, MD

Reference
Hughes-Cassidy F, Wong J, et al. Transient Homogeneously Enhancing Hepatic Masses: Can Size Predict Benignity? Am J Roentgenol; 2008; 190 (February): 300-307.