Adrenal Metastasis of Hepatocellular Carcinoma With Unknown Primary: A Case Report

Solitary extrahepatic hepatocellular carcinoma (HCC) with an unknown primary has been rarely reported in the literature. We report a case of a 69-year-old Hispanic male with no history of malignancy presenting with a solitary 5cm adrenal mass found incidentally on CT surveillance for high-risk liver disease secondary to chronic hepatitis C (HCV). Biopsy returned as metastatic poorly differentiated hepatocellular carcinoma. A dedicated liver MRI was performed to evaluate for a primary site, but no dominant lesion was noted. Follow-up abdominal CT two months later revealed interval enlargement of the mass to 6.2cm with an alpha-fetoprotein (AFP) of 169 ng/ml. After a multidisciplinary discussion, this was deemed a tumor of unknown primary. The patient was offered definitive treatment with stereotactic body radiotherapy (SBRT) 60 Gy in 8 fractions, with careful attention paid to the stomach, resulting in undercoverage of the lesion. AFP levels were used to track treatment efficacy and disease response. Retesting of AFP three months later was 20 ng/ml. CT imaging at the three-month follow-up was also consistent with a marked decrease to 3.6 cm from 6.2 cm. 27 months after treatment completion, the patient remains without signs of disease progression and normal AFP of 14.4 ng/ml without any clinical or radiographic signs of recurrence. HCC with solitary extrahepatic presentation is rare. Treatment with SBRT alone, and no systemic therapy, to an extrahepatic metastasis can yield excellent local and biochemical control, as expected based on the literature for primary SBRT to HCC lesions. This case underscores the importance of cautious attention to sparing of normal organs at risk, such as the stomach, since HCC tumors can respond to subablative doses. High-dose SBRT can be used to definitively treat oligometastatic hepatocellular carcinoma with an unknown primary tumor; however, longer-term follow-up will be needed to assess local control and whether new metastases arise.