Bone metastases in hepatocellular carcinoma: an emerging issue.

The nature and the characteristics of bone metastases (BMs) in hepatocellular carcinoma (HCC) have not been fully explored in literature, presumably because HCC skeletal involvement was rarely diagnosed until a few years ago. Recently, the prognosis and the management of HCC clinical progression have been improved thanks to novel imaging techniques and multidisciplinary treatment approaches. As in other osteotropic cancers, both angiogenesis and the epithelial-to-mesenchymal transition play a crucial role in skeletal colonization, with the cooperation of additional factors including vascular endothelial growth factor, transforming growth factor beta, platelet-derived growth factor, insulin-like growth factors I and II, bone morphogenetic proteins, secretory protein clusterin, and others. BMs from HCC are often characterized by soft-tissue expansion with an abundant vascular component and elevated tumor burden. As the majority of metastatic bone lesions from HCC are osteolytic, they are detectable by computerized tomography only at a late stage and not usually visualized by traditional bone scintigraphy. For this reason, new imaging tools are currently being investigated, such as dual tracer positron emission computerized tomography. HCC is frequently complicated by liver failure, resulting in a lower tolerance to opioids used for pain control, but radiotherapy and other local-regional treatments are useful in the treatment of BMs from HCC.