Ultrastructural findings in adrenal cortical adenomas clinically mimicking pheochromocytoma: a comparison with other adrenal tumors and tissue preparation techniques.

Adrenal cortical tumors clinically mimicking pheochromocytomas are extremely rare, with 14 cases in the literature. The authors describe 2 patients with adrenal cortical adenoma (ACA) and catecholamine elevations. The impact of tissue preparation methods on electron microscopy (EM) images was assessed in ACA mimicking pheochromocytoma, pheochromocytoma, and ACA lacking pheochromocytoma-like symptoms. Ten adrenal cortical tumors were examined using EM after a variety of tissue preparation techniques, including fixation with glutaraldehyde, formalin for varying lengths of time followed by glutaraldehyde, and/or formalin followed by paraffin embedding. Electron micrographs were assessed for image quality and the presence of dense secretory granules and eccentric, norepinephrine (NE)-type granules. Images created from tissue fixed in glutaraldehyde and/or formalin and embedded in resin were of good quality, while those derived from paraffin-embedded specimens were poor with disrupted cellular architecture. When pheochromocytoma was fixed in glutaraldehyde for 24 h or in formalin for 8 days, eccentric granules were identified. These granules were absent when tissue was fixed in formalin for 20 days or was obtained from a paraffin block. ACA without pheochromocytoma-like symptoms and ACA mimicking pheochromocytoma both had noneccentric dense-core granules on EM regardless of tissue preparation, and eccentric NE-type granules were absent. ACA is a rare cause of pheochromocytoma-like symptoms. These tumors lack eccentric, NE-type dense-core granules present in pheochromocytoma. Glutaraldehyde alone or formalin fixation followed by glutaraldehyde produces electron micrographs that may aid in the diagnosis of adrenal cortical tumors, whereas formalin-fixed, paraffin-embedded tissue results in images that are inadequate.