Spindle cell oncocytomas of the pituitary gland

Spindle cell oncocytomas (SCO) of the pituitary gland, also referred as adenohypophysis spindle cell oncocytomas, are rare, relatively benign (WHO grade I), and nonfunctional tumors commonly showing clinical and radiologic presentations mostly indistinguishable from the much more common non-secretory pituitary macroadenomas.


Spindle cell oncocytomas are estimated to represent only 0.1 to 0.4% of all sellar tumors and to occur more frequently in the 6th to 8th decades of life, with no gender preference .

Clinical presentation

As it happens with pituitary macroadenomas, spindle cell oncocytomas also commonly present with visual impairment, panhypopituitarism, and headaches .


They have been only recently listed on the WHO classification of the central nervous system tumors, in the fourth edition from 2007 .

The histogenesis of this tumor remains unclear, with some authors inferring that it derives from the folliculostellate cells of the adenohypophysis .  Microscopically, these tumors demonstrate bundles of spindle cells with an eosinophilic and granular cytoplasm. Immunohistochemistry is essential for their diagnosis, usually being positive for vimentin, S-100, EMA, and galectin .  Electronic microscopy will show swollen mitochondria, a reduced number of lysosomes, and rough endoplasmic reticulum .

Radiological features

These tumors can be intrasellar, with or without a suprasellar component . Less frequently, they can invade the cavernous sinuses, destroy the sellar floor, and extend into the sphenoid sinus .

They have a richer blood supply than that of pituitary adenomas, such that intraoperative bleeding poses a greater risk.


Reported as having the appearance of a solid mass isodense to the brain parenchyma.

  • T1/T2
    • ​​isointense to the brain parenchyma on T1
    • linear flow voids: represent blood vessels
    • hypointense foci: thought to represent hemosiderin deposits
  • T1 C+ (Gd): intense heterogeneous early enhancement, in contradistinction to macroadenomas, which enhance more slowly and not as avidly

Treatment and prognosis

The surgical approach is done with a transsphenoidal resection. γ-knife treatment or radiotherapy can be considered for the recurrent cases . Post-treatment imaging follow-up is recommended as up to a third of the cases have been reported to recur .

History and etymology

Roncaroli et al. first described the pituitary oncocytomas in 2002 .

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