PMC4996628_01
CT image. Transverse cut in cortical phase. An enhancing renal mass (black arrow) is seen at the upper pole of the right kidney and is abutting the lateral limb of the right adrenal gland.
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We obtained a CT renal mass protocol, which revealed a largely exophytic 2.7 cm enhancing mass at the anterolateral aspect of the upper pole of the right kidney (Fig. 1).
Pathologic findings establishing diagnosis. (A) The tumors were composed of solid nests of plump cells with variable clear and eosinophilic cytoplasm without atypia, necrosis, or mitosis. (B) Adjacent to the tumor, a plaque-like area of intrarenal adrenal rests is seen (white arrows) unassociated with the adjacent adrenal gland (black arrow). (C) No capsule is seen between the adrenocortical adenoma (white arrows) and adjacent kidney. (D) Confirmatory of adrenal origin, Melan-A is diffusely positive in the adenoma tissue (white arrows) but not in the adjacent normal renal tubules.
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On histologic sections, the solid nodule consisted of variably clear and eosinophilic cells with nested growth and without atypia, necrosis, or invasion, supportive of classification as an adenoma (Fig. 2A). In the renal parenchyma adjacent to the lesion were aberrant intrarenal adrenal rests, visibly separated from the adjacent, otherwise normal adrenal gland (Fig. 2B). Supportive of the adenoma arising from the intrarenal adrenal rests, there was a lack of encapsulation at the interface with the normal kidney (Fig. 2C). Confirmatory of adrenal origin and excluding a primary renal neoplasm, the tumor was diffusely positive by immunohistochemistry for Melan-A, an adrenal marker (Fig. 2D), and negative for PAX8, a sensitive marker of renal origin.