An unusual case of solid hamartoma in the liver

An unusual case of solid hepatic hamartoma, which could not be correctly categorized under the WHO classification, is reported. The well defined, solid nodular lesion, arising in the anterior edge of the left hepatic lobe, was found in a 15-month-old female infant. The lesion was composed of irregularly shaped yellow islands of parenchyma and white-gray nodules of fibrous stroma of various sizes, which were intermingled revealing a mosaic pattern. Prominent bile ductal proliferation was observed histologically in the fibrous stroma, associated in parts with dense or loose periductal bundles and vascular proliferation. The stromal proliferation seemed to result in erosion of the islands of differentiated parenchymal cells with no regeneration. Alpha-fetoprotein was demonstrated immunohistologically in the parenchymal cells of the lesion. From these findings, the essential component of this solid hamartoma was thought to be markedly proliferating bile ducts associated with periductal fibrosis, resulting in a fibroadenomatous pattern.