The cause for T2-weighted hypointensity may not be, however, always recognized, and only pathologic correlation may provide the answer.
The conjunction of other MR imaging findings and their integration in the clinical setting may allow a correct diagnosis in a considerable proportion of cases. On fat-suppressed T2-weighted images, nodules with a lipomatous component, such as lipoma, angiomyolipoma, hepatocellular adenoma, and hepatocellular carcinoma may also appear partially or totally hypointense. Examples include cases of focal nodular hyperplasia, hepatocellular adenoma, hepatocellular carcinoma, metastases, leiomyoma, siderotic or dysplastic nodules, nodules in Wilson disease, granuloma, and hydatid cyst. Although rare, low signal intensity relative to surrounding liver on T2-weighted images may be seen in a wide spectrum of lesions. Causes for this uncommon appearance include deposition of iron, calcium, or copper and are related to the presence of blood degradation products, macromolecules, coagulative necrosis, and other conditions. Rarely, however, hepatic nodules may appear totally or partially hypointense on those images.
The vast majority of focal liver lesions are hyperintense on T2-weighted magnetic resonance (MR) images.
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