Tumors invading the cavernous sinus that cause internal carotid artery compression are rarely pituitary adenomas.

There is a clinical impression that when tumors invade the cavernous sinus, compression of the internal carotid artery is rare with pituitary adenomas and more common with other types of lesions but there are no actual data to support this impression. To confirm the impression that the finding of internal carotid artery compression by tumors invading the cavernous sinus is inconsistent with a diagnosis of a pituitary adenoma, we performed a retrospective analysis of MRI scans performed between 2000 and July 2009. An initial search of the radiology database was performed using the terms "invasive mass cavernous MRI" and subsequent refinement narrowed the evaluation to 141 patients with cavernous sinus invasion by sellar/parasellar tumors for whom there were clinical/pathological data to determine tumor type. 83 of the 141 patients with cavernous sinus invasion had carotid artery encasement; 58 were pituitary adenomas and 25 were other types of lesions. Eight of these 83 scans revealed compression of the internal carotid lumen, with only one being a pituitary adenoma and seven being other types of lesions. Therefore, only 1/58 (1.7%) of pituitary adenomas and 7/25 (28%) of non-pituitary adenoma lesions that encased the internal carotid artery caused compression of the artery (P = 0.0007). A mass lesion that invades the cavernous sinus and encases the internal carotid artery is very unlikely, therefore, to be a pituitary adenoma if it compresses the lumen of the internal carotid artery.