A large adrenocortical adenoma surrounded with a renal arteriovenous malformation.

INTRODUCTION: Large adrenal adenomas are clinically rare. We report a case of a large adrenal adenoma with a renal arteriovenous malformation, mimicking a malignant adrenal tumor in preoperative imaging. CASE PRESENTATION: A 66-year-old woman presented to a local hospital with abdominal pain. A right adrenal tumor was detected, 66 mm in diameter and surrounded by thick and tortuous vessels. Based on the imaging findings, pheochromocytoma was suspected. However, clinical symptoms and endocrine abnormalities were absent, and radionuclide accumulation in scintigraphy was negative. Laparoscopic right adrenalectomy was performed. Intraoperatively, a notable growth of vessels forming a nidus surrounding the tumor was observed. Pathologically, this was diagnosed as an adrenocortical adenoma in conjunction with a renal arteriovenous malformation. CONCLUSION: We report a case of a large adrenal tumor surrounded with an arteriovenous malformation. To the best of our knowledge, this is the first reported case of this combination.