Are nonfunctioning pituitary adenomas extending into the cavernous sinus aggressive and/or invasive?

OBJECTIVE: We studied nonfunctioning pituitary adenomas extending to the ca vernous sinus to gain insight into the discrepancy between their histologic ally benign nature and frequent extension into the cavernous sinus. METHODS: We studied 10 patients with nonfunctioning pituitary adenomas that completely encircled the cavernous carotid artery (extension group). All 1 0 patients underwent surgery to remove intrasellar and/or suprasellar parts of the adenomas. Ten patients with nonfunctioning pituitary adenomas witho ut cavernous sinus extension comprised the control group. Tumor size follow -up data were obtained by magnetic resonance imaging. Immunostaining was pe rformed for Ki-67, cathepsin B, and matrix metalloprotainase-9. To assess t he wall thickness, 10 cavernous sinuses were removed from the cranial base of adult cadavers, and the walls were examined histologically. RESULTS: Magnetic resonance imaging demonstrated no remarkable growth in mo st of the patients during the follow-up period (mean, 65.8 mo). There was n o statistical difference in Ki-67, cathepsin B, and matrix metalloprotainas e-9 immunostaining between the extension group and the control group. The c adaver study demonstrated that the medial wall was significantly thinner th an the superior and the lateral walls (P < 0.0005). We found small defects in the capsule histologically in 3 of 30 sections. CONCLUSION: Our results indicate that most of nonfunctioning pituitary aden omas extending into the cavernous sinus are neither aggressive nor invasive . The high incidence of cavernous sinus extension of benign adenomas may be caused by the weakness of the media[ wall of the cavernous sinus.