Spindle cell oncocytoma of the sella turcica with anaplastic features and rapid progression in short-term follow-up: a case report with proposal of distinctive radiologic features.

We present a rare case of spindle cell oncocytoma (SCO) of the sella turcica with malignant histologic features and rapid progression. A 42-year-old woman experienced bilateral blurred vision and was preoperatively misdiagnosed as having a pituitary macroadenoma on magnetic resonance imaging. After surgery, SCO was diagnosed by the histopathologic features of interlacing fascicles of spindle tumor cells with finely granular, eosinophilic cytoplasm. Focal anaplastic changes and necrosis were present. Immunohistochemically, the tumor cells were positive for vimentin, epithelial membrane antigen, S-100, galectin-3, and thyroid transcription factor 1. Four months later, the tumor had progressed, and second surgery with adjuvant radiotherapy was performed; the patients remains under observation. In this report, we proposed distinctive radiologic features for differential diagnosis between SCO and other pituitary tumors.