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. 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.