Figure 5.

Pituitary tumors; histological and immunohistochemical characterization. Macroscopically, pituitary tumors were large, well circumscribed, solid, brown, masses located in the diencephalic area (Panel (A)). Montage showing the extra-axial homogeneous tumor with a prominent vascular network (Panel (B)). Low power view of a well-circumscribed, extra-axial neoplasm, which does not infiltrate the brain parenchyma (Panel (C), H&E, original magnification ×100). At higher magnification the tumor is composed of numerous pleomorphic cells with irregular nuclei and abundant eosinophilic cytoplasm. Giant multinucleated cells are present (Panel (D), H&E, original magnification ×400). Immunohistochemistry for chromogranin shows extensive cytoplasmic expression in neoplastic cells (Panel (E), original magnification ×200). Occasionally, neoplastic cells showed robust immunoreactivity for prolactin (Panel (F), original magnification ×400). Expression of the JCPyV early product, T-Antigen was found in the nuclei of numerous neoplastic cells, including giant multinucleated cells (Panel (G)), and p53 was also detected in the nuclei of tumor cells (Panel (H), both panels original magnification ×400).