Squamous cell carcinoma developing in an intracranial prepontine epidermoid cyst

Intracranial epidermoid cysts represent around 0,2 to 1% of all intracrania l tumours. Rare malignant transformation of these benign lesions may occur. A 66-year-old man presented with a state of confusion. MRI demonstrated a heterogeneous signal in front of the pens and ventricular dilatation. Cereb rospinal fluid examinations disclosed inflammatory cells. The patient died six months after his first admission to hospital. At autopsy, a firm greyis h tumour (3 cm-long and 1 cm-thick) was present in front of the brain stem encasing the basilar artery. Microscopic examination revealed a well-differ entiated epidermoid carcinoma arising from a cystic lesion whose wall was l ined by a squamous epithelium with a benign appearance. The walls of all th e ventricles were lined by carcinomatous cells. There was no leptomeningeal metastasis. Twenty three other cases of such squamous cell carcinoma have been reported and most of them had died within a few months.