What is the abnormality and what is the most likely diagnosis?
A large mass centred on the pituitary region most likely represents a pituitary macroadenoma.
MRI is the modality of choice. What are the usual sequences and planes for an MRI protocol?
Coronal and sagittal are the preferred planes, and usually T1 and T1 with contrast are obtained. A coronal T2 image is also often useful. With a lesion this large dynamic imaging is not particularly useful, although sometimes it is able to identify normal pituitary tissue when the mass turns out not to be a macroadenoma.
A large homogenous hyperdense mass arises from the pituitary fossa, resulting in erosion of the lateral aspect of the dorsum sellae. There is a protrusion pointing posteriorly from the left lateral aspect of the mass passing distal to the posterior wall of the dorsum sellae and abutting the left superior cerebellar artery. There is effacement of the suprasellar cistern.