Implications of very high serum prolactin levels associated with pituitary tumors.

Five patients with pituitary tumors associated with unusually high serum prolactin levels are presented. Tumor size and the presence of suprasellar extension were variable, but the finding common to all five cases was invasion of the cavernous sinus. It is proposed that very high serum prolactin levels suggest an invasive tumor, perhaphs, specifically, invasion into a cavernous sinus. The surgical significance of this proposition is discussed.