Spindle cell oncocytoma, a misdiagnosed rare entity of the pituitary – A case report with review of literature and special emphasis on the morphological differentials

Spindle cell oncocytoma (SCO) of the pituitary is a rare tumor of the adenohypophysis occurring in the sellar/suprasellar region. This tumor has been recognized as a distinct entity by the WHO Classification of CNS tumor in 2007. Spindle cell oncocytoma of the pituitary gland accounts for 0.1–0.4% of all sellar region tumors and is predominantly seen in the older adult population. This rare entity simulates clinical and radiological features of pituitary adenoma and is often misdiagnosed. Though WHO grade 1, the tumor can recur and have invasive properties. Herein, we report a 61-year-old woman with panhypopituitarism and temporal field cut, clinically and radiologically diagnosed as pituitary macroadenoma, while the histomorphological and immunohistochemistry features helped in arriving at a diagnosis of Spindle Cell Oncocytoma. The clinicopathological, histomorphological, immunohistochemical, and molecular properties of the tumor are further discussed.