Answer: Myelolipoma

Histology: Within the adrenal there is a highly cellular proliferation of normal hematopoetic elements associated with fat. One sees megakaryocytes, a spectrum of maturing granulocytes, and islands of erythroid precursors. These are the typical features of a myelolipoma.

Discussion: Granulocytic sarcoma would feature sheets of primitive granulocytic cell precursors. Diffuse large B-cell lymphoma would feature sheets of pleomorphic lymphocytes with irregular nuclear contours and prominent nucleoli. Adrenal cortical carcinoma would demonstrate more polygonal cells with eosinophilic cytoplasm, reminiscent of the cytology of the normal adrenal cortex. Adrenal cortical carcinoma demonstrates cytologic atypia, and characteristically shows vascular and capsular invasion. Myelolipomas which are fat-poor, like the current case, are often difficult to distinguish from other adrenal lesions by imaging.