What is the likely diagnosis? What are some differentials?
Pituitary macroadenoma is most likely. A meningioma should be considered. A craniopharyngioma should be included although they are usually not so uniform in density.
Does the enhancement pattern help distinguish between a macroadenoma and a meningioma?
Yes. Meningiomas usually enhance very vividly (more than this) where as this intermediate enhancement is typical for a macroadenoma.
CT demonstrates a large mass centred on the central base of skull, in the region of the pituitary fossa. A slightly hyperdense component extends superiorly indenting the floor of the third ventricle. The mass demonstrates moderate enhancement and encases both carotid arteries. The bone is remodelled and thinned with areas appearing deficient inferiorly.