Pituitary macroadenoma - encasing carotid
The patient went on to have surgery.
The biopsy shows a tumor composed of sheets, nests and cords of intermediate-sized cells with pale cytoplasm. Admixed with the tumor are numerous cholesterol clefts with surrounding giant cells. There are scattered hemosiderin deposits as well.
Immunohistochemical stains show the tumor cells are strongly positive for synaptophysin and negative for chromogranin. There are rare cells positive for ACTH and prolactin and a small cluster of cells positive for LH/FSH. Other stains are negative. The vast majority of cells are negative for all markers except synaptophysin. This is tumor is best considered a null cell adenoma.
The finding of cholesterol clefts with granulomatous reaction is very unusual in pituitary adenomas, but has been previously reported in the literature and is thought to be secondary to focal infarction of the tumor 1.