Pancoast Syndrome Due to Metastatic Hepatocellular Carcinoma.

Pancoast tumors are aggressive and locally invasive apical lung cancers that often compress and infiltrate adjacent structures including the brachial plexus, stellate ganglion, ribs, and vertebral bodies. Symptoms of Pancoast tumors include Pancoast Syndrome, characterized by Horner Syndrome and pain and weakness of the ipsilateral upper extremity. Pancoast tumors by definition are primary lung cancer and are nearly always non-small cell lung cancer (NSCLC). There are rare case reports of metastatic non-pulmonary malignancies forming apical lung tumors mimicking Pancoast tumors and causing Pancoast Syndrome. Here, we present a case of a 66-year-old male with a history of unresectable hepatocellular carcinoma (HCC) who presented with one year of progressive left wrist and forearm pain and hand weakness and was found on cross-sectional imaging to have a left upper lobe lung mass invading the T1 and T2 vertebral bodies. Pathology showed very poorly differentiated carcinoma that required specialized testing to achieve diagnostic clarity. The tumor was positive for albumin mRNA, which aided in confirming the lung mass as metastatic HCC. This case highlights a rare incidence of Pancoast Syndrome due to metastatic HCC and emphasizes the importance of considering this diagnosis as an etiology of left upper extremity pain in a patient with previously diagnosed malignancy. This case also demonstrates the utility of albumin mRNA in-situ hybridization as an additional tool in identifying metastatic HCC and reviews general principles of symptomatic management of Pancoast Syndrome.