Development of fat within a meningioma.

We report a tentorial meningioma containing fat. Multiple areas of fatty density or intensity in the tumour were seen on CT and MRI, which corresponded histologically to lipomatous components. CT 10 years previously had demonstrated a smaller tumour without evidence of fatty components. We found only five cases in the literature in which fatty density was demonstrated within a meningioma on CT and a lipomatous component histologically proved. Xanthomatous change, with lipid in tumour cells, causes decrease in density on CT, but not to the levels of fat. As both lipomatous components and xanthomatous change show similar intensity on MRI, CT can be helpful in differentiating these two conditions. To our knowledge, our case is the only one in which the advent of fatty tissue was confirmed during follow-up.