A rare and challenging case of extrahepatic costal metastases from an unknown primary hepatocellular carcinoma

Hepatocellular carcinoma (HCC) typically presents with a primary hepatic mass. Nevertheless, on rare occasions, the initial presentation can be exclusively related to extrahepatic metastases and the most common sites of metastases are the lungs, lymph nodes, bones, and adrenal glands. While, bone metastases are generally accompanied by multiple metastatic spreads elsewhere in the body or previously diagnosed HCC, cases of solitary bone metastases with no liver lesion at imaging have been reported. Indeed, two rare entities of HCC have been reported in the literature which are the ectopic hepatocellular carcinoma and the infiltrative type of hepatocellular carcinoma with a very challenging radiologic diagnosis and poor prognosis. In this article, we present a case of extrahepatic costal metastases of hepatocellular carcinoma, which was diagnosed through a bone biopsy, with no focal lesion on liver imaging including ultrasound, multiphase MRI, and CT scan except for the presence of a portal vein thrombosis. It is important to consider the possibility of HCC metastases when evaluating rapidly growing extrahepatic lesions in patients with chronic liver disease and to consider the tumor characteristics and imaging findings as well as limitations to make accurate and timely diagnosis leading to improved patient management. Our patient had probably an infiltrating HCC because of two prominent factors: the presence of portal vein thrombosis and a markedly elevated alpha-fetoprotein (AFP). A liver biopsy was crucial in order to confirm the diagnosis but unfortunately it could not be performed because of the unexpected death of the patient due to hemorrhagic shock. It is also worth noting in this case, that the elevated level of AFP raised the suspicion on an underlying HCC and contributed to more elaborate diagnostic tests.