Background: Adrenal cysts are rare lesions that may pose significant diagnostic challenges, particularly when they are large and located in close proximity to adjacent organs such as the liver and kidney. Endothelial cysts represent one of the most common histological subtypes of true benign adrenal cysts.

Case presentation: We report the case of a 33-year-old female patient presenting with a large right-sided cystic mass measuring 15x10 cm, initially interpreted as a hepatic hydatid cyst as an adrenal origin was not suspected preoperatively. A right adrenalectomy was performed through an open approach, histopathological and immunohistochemical examination demonstrated a benign adrenal endothelial cyst with positive CD34 staining.

Conclusion: Giant adrenal endothelial cysts may mimic hepatic hydatid cysts, particularly in endemic regions, due to the close anatomical relationship between the right adrenal gland, liver, and kidney. This case highlights the limitations of preoperative imaging in determining the exact organ of origin of large retroperitoneal cystic masses and emphasizes the crucial role of histopathological examination in establishing the definitive diagnosis.