Nodular lesions associated with abnormal liver circulation.

In order to present new findings of imaging studies and pathology, we describe nontypical lesions rather than well-known typical lesions such as focal nodular hyperplasia (FNH), hepatocellular adenoma, nodular regenerative hyperplasia (NRH) and large regenerative nodules in liver with idiopathic portal hypertension (IPH). Nontypical lesions are not definitively diagnosed as any of the above typical well-known lesions. These lesions are not rare, and are clinically important since they must be differentiated from hepatocellular carcinoma. These lesions can be formed by hyperperfusion of either the artery or the portal vein. They are found in either the hilar area or peripheral area. The extranodular liver (background liver) shows various histological findings, being nearly normal in some cases but showing a clearly abnormal vasculature in others. The lesions, therefore, present various patterns in imaging. Pathological examination also shows variation in the size of the lumen of portal veins and arteries. Abnormal arrangement of arteries and portal veins are also demonstrated, while parenchymal nodular liver tissues are uniformly nonneoplastic benign hyperplastic tissues. These nontypical lesions and well-known typical lesions (FNH, NRH and IPH) are explained by a single etiological mechanism of anomaly of the portal tract. They can be collectively called anomalous portal tract syndrome. For their definitive diagnosis, the structure and hemodynamics of the nodules need to be clarified by images. Biopsy is also necessary to confirm that the lesions consist of benign hepatic tissues. Subsequently, these findings should be evaluated comprehensively.