The identification of small nodules in liver adenomatosis

Liver adenomatosis is characterized by the presence of multiple adenomas of various sizes in the liver. The aim of this study was to characterize the morphology of small nodules which can be difficult to identify.

Seven patients included in this study underwent surgery for the removal of one or several nodules. All, but one, were females. Three out of seven presented with acute bleeding. Five had six or more nodules at presentation, and two only one, who developed nodules later on during follow-up.

All of the large nodules that were >2 cm, except one, were typical adenomas with or without hemorrhagic areas. Smaller nodules (1-2 cm), some of which discovered on the resected specimen were either typical adenomas or non-typical nodules. These non-typical nodules were characterized by a polylobulated aspect with steatotic zones, and in between, bands of non-steatotic hepatocytes with portal tracts-like structures containing occasional cytokeratin 7 and less often cytokeratin 19 positive biliary cells. Numerous steatotic foci were also seen in four cases. They were isolated or grouped forming microadenomas or non-typical micronodules (<1 cm) containing biliary elements. Our findings lead to the following hypothesis: adenomatosis is characterized by the simultaneous occurrence of multiple adenomas; if several adenomatous foci expand at the same time in the same area, they will form one polylobulated nodule containing non-adenomatous tissue with portal tracts in between areas of adenomatous tissue (non-typical micronodule). Such a small micronodule may in turn expand and join another micronodule to form a bigger one by the same process (non-typical nodule). As nodules grow, their non-adenomatous components including hepatocytic plates and portal tracts constituents will progressively disappear to end up with the classical aspect of an adenoma.

This hypothesis supports the concept that non-typical nodules/micronodules are adenomas precursors. However, they can be difficult to classify since they resemble focal nodular hyperplasia precursor.