506 Adenomatoid Tumor of the Liver: A Rare Benign Tumor

Introduction/Objective Adenomatoid tumors(AT) are benign neoplasms typically found in the reproductive tracts. Their occurrence in extragenital sites is extremely rare. This study presents a rare case of a hepatic AT in a 75-year-old female. Methods/Case Report A CT-scan working up a recurrent abdominal hernia revealed a 7.7 cm heterogeneously hyper-enhancing mass in the liver. The patient, a former smoker with COPD, underwent a CT-guided liver biopsy. Histology showed foci of small epithelioid cells with clear cytoplasm in a background of capillary-sized blood vessels. Immunohistochemical staining was positive for pancytokeratin, CK7, and calretinin, and negative for endothelial, neuroendocrine, and other lineage-specific markers. A preliminary diagnosis of Low-Grade Epithelioid Neoplasm was made due to limited biopsy material, although the possibility of AT was raised due to bland morphology and calretinin positivity. A subsequent wedge resection revealed a hemorrhagic, well-circumscribed lesion composed of tubular structures within fibromyxoid stroma. Tumor cells were negative for CD34 and CD31 but positive for calretinin and WT1, supporting a mesothelial origin. A tertiary academic center confirmed the diagnosis of hepatic AT. Results NA Conclusion This rare case highlights the importance of considering AT in the differential diagnosis of liver masses. As well, it highlights the importance of immunohistochemical staining in its timely diagnosis.