Lymphoma of the skull

A large hyperdense mass that has a large intracranial component and a smaller extracranial component preserving the intervening bone. Extensive oedema and mass effect. No hyperostosis or bony destruction (best seen on bone windows that are not, unfortunately, available). 

A large intracranial lesion is present within the right frontal region that crosses bone with an associated extracranial component that involves the right temporalis muscle and extends inferiorly into the infratemporal fossa.

The lesion is isointense to grey matter on both T1 and T2, and demonstrates heterogeneous peripheral and central regions of enhancement. At the medial and posterior margins of the lesion, T1 hyperintensity measuring up to 9 mm in depth with associated susceptibility artefact is in keeping with surrounding haemorrhage. Further regions of susceptibility artefact also noted within the medial and inferior portions of the lesion. More medially is an additional region of peripheral contrast enhancement surrounding an area of "cystic" change. Dural tails are present.

Extensive surrounding T2/FLAIR hyperintensity, with associated localised mass effect and effacement of the right lateral ventricle, with midline shift to the right.

The right frontal bone demonstrates slightly increased T1 signal and decreased T2 signal.

Both the intra and extracranial lesions demonstrate marked diffusion restriction. MR spectroscopy is non-specific, especially given the extensive susceptibility artefact. Mildly elevated CBV is noted, similar to adjacent grey matter.

No other intracranial lesions identified.

Conclusion:

Solitary large right frontal intracranial haemorrhagic lesion involving bone, and with an extracranial component, is most likely extra-axial (either bone or dura) in origin. Although this lesion is not entirely typical for a particular diagnosis, lymphoma or an atypical/anaplastic meningioma (highly cellular). Haemangiopericytoma, metastasis, and primary sarcoma are other possibilities.