Large prolactin-secreting tumors are rare and their endocrinological and surgical management may be complex. We report the case of a patient with a prolonged history of unilateral tinnitus and sensation of a stopped-up ear who had a very large, invasive and aggressive tumor of the sphenoidal region with bone destruction, invasion of structures in every direction from the sellar region and extracranial extension to the ethmoid and nasopharynx. Serum prolactin level at the time of diagnosis was 16,860 ng/ml (normal: 3-17 ng/ml). Medical treatment with bromocriptine reduced the prolactin level to 31 ng/ml and reduced the size of the tumor, although less than expected. The literature is reviewed and the rarity of such large, invasive prolactinomas is highlighted, as well as the absence of symptoms and signs suggesting the presence of such a large tumor of the skull base.