PMC7537674_01
Macroscopic specimen: tan-brown neoplasm with regular and smooth borders largely replacing the normal adrenal gland parenchyma, which is recognizable at the margin of the specimen.
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The surgical specimen underwent histopathological examination: it consisted of adipose tissue containing a tan-brown neoplasm, with regular and smooth margins, of 2.7 x 2 cm in size, largely replacing the normal adrenal gland parenchyma (Figure 1).
Histopathological features and immunohistochemical findings: (a) encapsulated diffuse proliferation of large cells with focal capsular invasion. Inset: the cells show pleomorphic nuclei, prominent nucleoli, and wide eosinophilic and granular cytoplasm. (b) At higher magnification, capsular invasion is shown in detail (the arrow signs a thin fibrous capsule dividing the neoplasm from the cortex of the adrenal gland, while the thick arrow shows the focal infiltration of the adrenal parenchyma by the tumour). (c) The neoplastic cells resulted negative for chromogranin A (positive internal control: adrenal medulla). (d) The neoplastic cells resulted strongly and diffusely positive for inhibin A (internal control: adrenal cortex, mild and sparse positivity). (a, b) Haematoxylin-eosin stain. (c) Chromogranin A. (d) Inhibin A. Original magnification: (a) 40x, inset 200x; (b) 200x, (c, d) 100x.
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Microscopically, the nodule was composed of more than 90% of an encapsulated proliferation of oncocytes (cells with large eosinophilic and granular cytoplasm, pleomorphic nuclei, and prominent nucleoli) in a diffuse architectural pattern (Figure 2(a) and inset). The tumour only focally showed capsular infiltration (Figures 2(a) and 2(b)). Immunohistochemical tests revealed that the tumour cells were negative for chromogranin A (Figure 2(c)) and positive for inhibin A, a specific marker of adrenocortical origin (Figure 2(d)).
Electron microscopy findings: (a) electron micrographs show adrenal oncocytoma cells, characterized by the presence of large amount of mitochondria (scale bar represents 2 mum). (b) high magnification displays ultrastructural details of crista-type mitochondria (scale bar represents 0.2 mum).
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Electron micrographs confirmed adrenal oncocytoma cells, characterized by the presence of a large amount of mitochondria (Figure 3).