Discrimination of Small Hepatic Hemangiomas from Hypervascular Malignant Hepatic Tumors with Three Phase Helical CT

Purpose: To compare the appearance of small hepatic hemangiomas at non-enhanced and contrast enhanced helical computed tomography (CT) with that of small ( 3 cm) hypervascular malignant tumors and to evaluate the accuracy of multiphase helical CT in such aspects.Patients and Methods: A total of 30 patients with small hemangioma like lesions detected by ultrasonographic scanning were examined using 3 phase helical CT images in the precontrastand after contrast material injection, in the arterial and portal venous phases. Radiologists evaluated the lesion type and degree of change in enhancement from arterial to portal venous phase. They rated their confidence in the discrimination of hemangiomas from malignant tumors. Diagnosis was established by means of histologic findings in specimens obtained at percutaneous biopsy, or MRI for hemangioma like in ultrasonography.Results: Ten HCCs were shown as nodular enhancement on early arterial-phase CT. The density of the whole tumor decreased rapidly on late and delayed phases, and the edge of 4 tumors (4/10) remained relatively hyperdense compared with the surrounding liver tissue, and demonstrated as rim enhancement. Rim enhancement was shown as 1 to 2-mm wide irregular, uneven and discontinuous circumferential enhancement at late, and delayed-phase of CT. Eight hypervascular metastases were noted (6 in breast carcinomas, 1 in renal cell carcinoma and 1 in neuroendocrine tumors). Twelve hemangiomas were found. Multiphase CT showed atypical pattern in 4 cases of small hemangiomas, (homogenus enhancement in arterial phase, 3 cases and non enhancement in 1 case). Readers diagnosed hemangiomas with 66% mean sensitivity with all enhancement phases and diagnosed malignant lesions with 96% mean specificity. Conclusion: Small hemangiomas frequently show atypical appearances at CT. Two-phase helical CT does not improve sensitivity but does improve specificity for differentiating hemangiomas from hypervascular malignant tumors. If initial us scanning of the liver depicts a hemangioma like lesions,especially in patients at risk, other confirmatory imaging studies are necessary since 50% of hemangioma in this study were hypervascular malignant tumors. Percutaneous biopsy can be safely performed and findings can be used to confirm the diagnosis.