The atoll sign in hepatic imaging has been described when a liver lesion shows a peripheral rim of high T2 signal intensity with the center of the lesion appearing isointense to the background of non-cirrhotic liver on T2WI mimicking an atoll. The peripheral rim shows hyperenhancement in the portal venous and delayed phases 2. It is considered a characteristic sign of an inflammatory hepatic adenoma but is only seen in about one-third of cases. It probably represents dilated sinusoids within the periphery of the adenoma.
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