Fig. 2.

Photomicrographs of the histological and immunohistochemical features of the primary pituitary tumor and the metastasized liver tumor. Pituitary tumor: a, c, e, and g; liver tumor: b, d, and f. Both pituitary and liver tumors show nuclear pleomorphism, hyperchromasia, and enlarged nucleoli (arrow heads) on hematoxylin–eosin staining, but neither tumor shows mitotic figures (a, b). There is diffuse cytoplasmic ACTH immunostaining in both tumors (c, d). Numerous tumor cell nuclei are positive for Ki-67, and the proportion of cells with positive Ki-67 staining accounts for 15% and 35% of the primary (e) and metastasized (f) tumor cells, respectively. Immunoreactive nuclear protein p53 examined in the primary pituitary tumor is stained in almost all cells (g). Original magnification ×400 (a, b), ×200 (c–g)