A focal bony defect on the right side of the clivus, with small arcs of bone located within and over the dorsal surface of the lesion. Intact bone, albeit thinned, is seen separating the lesion from the sphenoid sinus. The posterior wall the pituitary fossa may however be deficient.
Conclusion: Off-centre well circumscribed high T2 signal lesion seen on MRI, has calcification/ossification of the matrix in arcs and spicules. This suggests a low-grade chondroid lesion (low-grade chondrosarcoma) over the alternative diagnosis of an ecchordosis physaliphora or even less likely a chordoma (given only minor growth over the past 2 years).