Answer: Adrenal myelolipoma

Histology: Most of this lesion is characterized by recent blood, fibrin, and associated calcifications. Focally a nodule of adrenal cortical tissue is seen within the surrounding adipose tissue with a somewhat infiltrative perimeter. The lesion lacks cytologic atypia, mitotic activity, and vascular invasion. Elsewhere in the lesion, there was one area representing less than 5% of the specimen and present on only a couple of slides demonstrating adipose tissue with associated myeloid elements.

Discussion: Large adrenal masses are often presumed to be adrenal cortical carcinoma given the size criteria difference between adrenal cortical adenoma and carcinoma. In the current case the presence of adrenal cortical tissue within the surrounding adipose tissue further suggested adrenal cortical carcinoma.

However, one may see adrenal cortical tissue in the surrounding peri-adrenal adipose tissue even in the normal adrenal gland and does not signify either a neoplasm or malignancy. The presence of focal myeloid elements associated with adipose tissue is diagnostic of myelolipoma. Adrenal myelolipomas may on occasion spontaneously bleed, which rarely may even be a fatal. Adrenal myelolipomas, however, are entirely benign. Often these lesions are not even removed as they can be diagnosed preoperatively based on the presence of fat on imaging studies.