Using immunoelectron microscopy with 10 nm protein A-gold complex, which we also used for growth hormone and prolactin in pituitary adenomas [18], CgA is confined to the secretory granules of islet cells revealing stronger density in α-granules than in β-granules, especially on the periphery of the granules, while SPY immunostaining is diffusely in the cytoplasm [1]. Here, CGA is linked to pituitary gland adenoma.