Adrenocortical oncocytoma: case report with immunocytochemical and ultrastructural study.

An adrenocortical oncocytic neoplasm was detected incidentally in a 58-year-old man. The tumour weighted 315 g, showing haemorrhagic areas and broad fibrous bands. It was composed exclusively of large eosinophilic cells packed with mitochondria showing flat and infrequent tubulovesicular cristae and regression of steroid-related organelles. Occasional annulate lamellae and mitochondrial osmiophilic inclusions were present. Vimentin was diffusely expressed, whereas AE1/AE3 cytokeratin was detected in half of the cells; a focal punctate pattern of staining was exclusively observed for cytokeratin peptides 8 and 18. The patient had no evidence of disease 21 months after surgery.