Background: Adrenocortical adenoma is a rare, benign neoplasm that originates from the adrenal cortex and its differentiation from renal masses is difficult in special cases of gigantic masses.
Case Report: We report a 38-year-old man with an incidental mass in the left upper quadrant of the abdomen. Computed tomographic (CT) scan revealed that the mass originated from the left adrenal and was highly suggestive of adrenal carcinoma. However, the histologic examination after adrenalectomy confirmed the mass to be an adrenocortical adenoma, not carcinoma, compressing the kidney.
Conclusions: The presence of a large adrenal tumor does not always indicate malignancy, even with the presence of malignant imaging phenotypic features. In these situations, the final key point is precise pathologic interpretations.

Keywords: Pheochromocytoma, Adrenal mass, incidentaloma, adrenal carcinoma, Adrenocortical Adenoma