[Hepatocellular nodular hyperplasias, adenomas and carcinomas].

Nodular hyperplasias ("hyperplasiomas") are new formations whose development as a required and regulated response can be traced either to compensatory reactions to the loss of cells (regeneration in a narrow sense) and to decreased cellular performance, or to primary growth impulses. Included in this group are: the "macroregenerative nodules" after extensive cell losses; solitary nodules of uncertain etiology; and the minute foci of "micronodular transformation" whose origin can be traced to a particular disturbance of the hepatic blood supply. The so-called "adenomatous hyperplasias" of the cirrhotic liver that have a tendency towards carcinomatous change are not included in this group and are perhaps better considered as "hyperplasiogenic adenomas". The so-called "focal nodular hyperplasia" too, it must be stressed, should be separated from the simple hyperplasias, for it is more closely related to the adenomas, but represents a new formation of limited growth potential. Morphologically it is conspicuously subdivided by multiple connective tissue bands and scars, but it is above all characterized by metaplastically derived neoductuli, and hence it is appropriately designated as a "combined nodule". Among the true uninodular adenomas there are several variants differing in their morphology,--the so-called "atypical" or "intermediate" forms, that can give rise to carcinomas. The hepatocellular carcinoma, that may arise in a variety of ways, presents multiple cytological and histological variants, but only the so-called "fibrolamellar carcinoma" presents also a clinical peculiarity. "Hepatoblastomas" differ from the common hepatocellular carcinomas by their origin in early childhood from immature early precursor cells and, in the later phases of life, from redifferentiated cells that can even give rise to mesenchymal elements. There is no evidence of the existence of particular pluripotential stem cells.