2474 Identification of Large Liver Mass of Unknown Origin

Abstract

INTRODUCTION: Liver lesions of unknown etiology are commonly encountered at tertiary referral centers. Differential diagnoses include both benign and malignant neoplasms. Most often, lesions can be identified based solely on characteristic imaging findings; however, in rare cases, biopsy should be considered for definitive diagnosis. Here we describe the diagnostic work up of a large liver mass secondary to metastatic uveal melanoma. CASE DESCRIPTION/METHODS: 65-year-old male with no personal or family history of liver disease who was referred for a large liver mass discovered during work up of progressive abdominal pain and weight loss. Patient reported moderate alcohol use (2-4 alcoholic drinks per night) but had no other risk factors for the development of liver disease. Physical exam revealed a large, tender mass crossing the abdominal midline. Labs unremarkable including normal tumor markers. Imaging revealed 14.7 cm mass taking up majority of the left hepatic lobe (Figure 1). Vibration controlled transient elastography showed a low stiffness score indicating very low likelihood for advanced fibrosis/cirrhosis. Case was discussed at multidisciplinary liver tumor board. Mass fulfilled all requirements of LI-RADS 5 lesion although LI-RADS designation did not apply as patient was not at elevated risk for hepatocellular carcinoma (HCC). No evidence of metastasis on initial imaging. Patient subsequently referred for possible left hepatectomy. Preoperative studies showed evidence of extensive metastases. Therefore, mass was deemed non-resectable. Patient consequently referred to Medical Oncology. Liver biopsy was performed which was consistent with metastatic malignant melanoma (Figure 2). Further staging studies showed hypermetabolic activity involving L orbital globe, bilateral lungs and liver indicating continued disease progression (Figure 3). Patient started on nivolumab and ipilimumab for rare metastatic uveal melanoma with extensive hepatic as well as lung metastases. Unfortunately, tumor remained very aggressive and patient died within 3 months of initial imaging findings. DISCUSSION: This case highlights the importance of good history taking and maintaining a broad differential during evaluation of a liver lesion of unknown origin. While this lesion met all diagnostic criteria for HCC, it was ultimately identified as metastatic melanoma. This underlines the sustained role of liver biopsy in indeterminate liver lesions in patients without liver disease.