Primary liver tumors: Diagnosis by MR imaging

MR features of 153 proved primary liver tumors (95 malignant, 58 benign) in 55 patients with hepatocellular carcinoma (21), cholangiocarcinoma (seven), carcinosarcoma (one), hepatoblastoma (one), hemangioma (16), hepatic adenoma (four), focal nodular hyperplasia (three), leiomyoma (one), and hemangioendothelioma (one) were studied retrospectively to determine which techniques are most reliable for lesion detection and which criteria are most useful for differential diagnosis. MR data were correlated with histologic features such as fatty degeneration, fibrosis, and peritumoral edema. Unlike metastatic cancer, hepatocellular carcinoma was best detected (p < .01) with T2-weighted pulse sequences. The mean tumor-liver T2 difference was 34.4%, while the mean T1 difference was only 21.8%. A tissue-specific diagnosis of hepatocellular carcinoma was possible in 14 of 21 patients by identification of fatty degeneration of the tumor (eight of 17), tumor capsule (five of 21), and/or vascular invasion (six of 21). MR features of peritumoral edema, present in six of 21 patients with hepatocellular carcinoma and in seven of 25 patients with metastases, were exclusively associated with malignant tumors. The large variation in tissue characteristics (relaxation times and proton density) seen in primary liver tumors necessitates the use of multiple pulse sequences to maximize lesion detection. However, the combined use of T1- and T2-weighted spin-echo and T2-weighted phase-contrast images had the advantage of distinguishing benign from malignant primary liver tumors in 48 of 55 patients in this series.