Is spindle cell oncocytoma a true entity or a variant of pituicytoma? A case report with review of literature.

Spindle cell oncocytoma (SCO) is a newly described rare entity simulating clinicoradiological features of a nonfunctional pituitary adenoma and is corresponding to the category of World Health Organization grade I tumor. However, because of the reported incidence of recurrence and invasive presentation in some cases, its categorization as a low grade tumor is questionable. Earlier, it was thought to arise from the folliculostellate cells of adenohypophysis. Recently, few reports have described expression of thyroid transcription factor-1 [TTF-1], which is a specific marker for pituicytes of neurohypophysis, suggesting this tumor to be a variant of pituicytoma. We describe a case of SCO in a 28-year-old young female patient with TTF-1 immunopositivity, and ultra-structurally showing abundant mitochondria along with few neurosecretory granules.