Fig. 2

The histological features of the resected tumor are consistent with those of chromophobe pituitary neuroendocrine tumor, and there is no plasma cell infiltration (a: hematoxylin–eosin staining, original magnification, 400 ×). Immunohistochemistry findings indicate that the tumor is positive for follicle-stimulating hormone-beta (b: original magnification, 400 ×). Immunohistochemistry findings indicate the tumor is positive for steroidogenic factor-1 in the cell nuclei (c: original magnification, 400 ×). Pathological examination results showing a marked infiltration of plasma cells into the anterior and posterior lobes (d: hematoxylin–eosin staining, original magnification, 400 ×), which is more than 10 IgG4-positive plasma cells per high-power field (e: immunohistochemistry for IgG4 monoclonal antibody, original magnification, 400 ×)