MKI67 and pituitary gland adenoma: Additional electron microscopy analysis showed granular secretory vesicles (Figure 3J and K) as are commonly observed in hormone producing pituitary adenomas (Figure 3M and N).The number of Ki67 positive cells (Figure 3L, Figure S4) ranged from less than 1% to up to 8.4% comparable to human pituitary specimens that typically show between 1% to 3.8% positivity (MIB index).