. Author manuscript; available in PMC: 2019 Nov 9.

Published in final edited form as: J Neurosurg. 2018 Oct 19;131(2):517–525. doi: 10.3171/2018.4.JNS18211

TABLE 4.

TTF-1–positive tumors of the posterior pituitary gland

Tumor Subtype	Histology & Ultrastructure (EM)	Immunoreactivity	Distinguishing Features
All		TTF-1 (strong nuclear immunoreactivity)^16,22 S100 (variable staining)
SCO	Spindle or epitheloid cells in intertwining fascicles w/ granulated eosinophilic cytoplasm; abundant mitochondria by EM	EMA (strong) GFAP (rarely positive)	Increased tendency to bleed during the op
Pituicytoma	Fibrillary cells arranged in fascicles w/ elongated nuclei; abundant intermediate filament processes by EM	EMA (variable) GFAP (positive generally)
Granular cell tumor	Polygonal cells w/ central nuclei & PAS-positive, granular cytoplasm; abundant lysosomes by EM	EMA (variable) GFAP (rarely positive)

EM = electron microscopy; PAS = periodic acid-Schiff.