Figure 3b-23: Histology of TTF-1 positive neoplasms of the neurohypophysis. Granular cell tumour (left) and pituicytoma (right) are morphologically distinct but share nuclear TTF-1 expression, confirming their origin from specialised glial cells of the posterior gland or infundibulum. Both entities are S100 positive but only the pituicytoma expresses GFAP.