S5757 Hemorrhagic Hepatic Cyst Mimicking Subcapsular Hematoma: A Rare and Complex Diagnostic Challenge

Introduction: Hepatic cysts are commonly incidental findings, often benign and asymptomatic. However, large or hemorrhagic cysts may mimic malignancy or subcapsular hematoma, presenting significant diagnostic and management challenges. We present a rare case of a massive hepatic cyst with spontaneous hemorrhage, elevated tumor markers, and compressive symptoms initially concerning for malignancy. Case Description/Methods: An 80-year-old woman with hypertension presented with right upper quadrant pain, weight loss, and hypoxia. Imaging revealed a complex 18.7 cm right hepatic cyst with internal blood products and associated pleural effusion. Tumor markers showed elevated CA 19-9 (1,743), with normal AFP and CEA. Initial aspiration was negative for malignancy. On readmission, worsening symptoms and enlarging cyst prompted CT-guided drainage of over 2 liters of hemorrhagic fluid, again negative for infection or malignancy. Right-sided thoracentesis yielded exudative fluid without evidence of malignancy. During hospitalization, the patient developed left leg deep vein thrombosis and underwent inferior vena cava filter placement due to contraindication to anticoagulation. She was discharged with a hepatic drain in place. Follow-up imaging showed interval cyst reduction (to ∼14 cm). CA 19-9 decreased to 32.7. Surgical consultation recommended laparoscopic fenestration if symptoms persisted. Discussion: This case highlights a rare presentation of a hemorrhagic hepatic cyst simulating a subcapsular hematoma or malignancy. Elevated CA 19-9 and complex imaging features initially raised concern for neoplasm. However, comprehensive evaluation and serial fluid analyses confirmed benign pathology. The case underscores the importance of integrating imaging, tumor markers, and fluid cytology in hepatic cyst evaluation. Additionally, complications such as deep vein thrombosis due to delayed anticoagulation require multidisciplinary coordination. Massive hemorrhagic hepatic cysts can mimic neoplastic or vascular pathology. Early diagnostic imaging, cautious fluid analysis, and appropriate follow-up are crucial for accurate diagnosis and symptom relief. This case adds to the limited literature on large hepatic cysts with hemorrhagic transformation.