Spindle cell oncocytoma of the adenohypophysis.

Spindle cell oncocytoma of the adenohypophysis (SCO) is defined as spindle to epithelioid cells with oncocytic appearance presenting in the adenohypophysis. In contrast to pituitary adenomas, the SCO does not show immunoreactivity for neuroendocrine markers and pituitary hormones but co-expressed vimentin, S-100 protein, epithelial membrane antigen (EMA), and antimitochondrial antibody MU213-UC clone 131-1. We describe an SCO in an adult, a 42-year-old woman whose magnetic resonance (MR) images documented an intrasellar lesion located in the hypophysis.