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Dysplastic nodules in liver cirrhosis: imaging

Dysplastic nodules (DNs) have diameters of 1 mm or larger, show abnormal tissue development, but lack definite histopathologic findings of malignancy [1]. In the clinical setting, a DN is defined as a nodular lesion that is significantly larger than other regenerative nodules in the cirrhotic liver. On pathologic specimen, a DN is usually a hepatic nodule measuring about 1.0 cm, with a yellow color. It has no true capsule. The nodule is soft in consistency but bulges out slightly on section [2]. The yellow tint of a DN is attributed mainly to the fat globules within the hepatocytes [2]. On histologic examination, the cell density is moderately increased compared with that of the surrounding liver. However, no evident structural abnormality is present. Because of the slightly decreased amount of cytoplasm, the ratio of the size of the nucleus to that of the cytoplasm is also slightly increased, although the size of the nucleus varies. The cord structure is often more prominent than the surrounding tissue [1]. DNs can be characterized further as low-grade dysplastic nodules (LGDNs) and high-grade dysplastic nodules (HGDNs) to denote the degree of atypia [3, 4]. HGDNs may have any of the features of LGDNs, but they also have one or more of the following: a high ratio of nuclear size to cytoplasmic size, nuclear hyperchromasia, irregular nuclear contour, rare mitotic figures, hepatic cell cords more than two cells wide, pseudoglandular formation, cytoplasmic basophilia, and resistance to iron accumulation. Invasion of stroma or portal tracts is absent. HGDN should be diagnosed if neoplastic features resemble those seen with malignancy. HGDNs usually contain fat globules in the cytoplasms, whereas LGDNs usually do not contain fat globules. The fat deposition in DNs may be related to malignancy because DNs containing malignant foci and early well-differentiated hepatocellular carcinomas (HCCs) contain much fat. Kojiro [2] speculated that fat deposition in a nodule is closely related to a developmental mechanism of DN to HCC.