[Primary intracranial malignant epidermoid--case report].

Intracranial malignant epidermoid is uncommon. We report a case of a 74-year-old woman with a primary intracranial malignant epidermoid in the parapontine region. The tumor was visualized as two components (a low-density benign prepontine lesion and a malignant enhanced cerebellopontine angle lesion) on CT scan. On MRI, the benign portion demonstrated low-signal intensity on T1 weighted images and markedly increased heterogeneous signal intensity on T2 weighted images, while the malignant portion showed iso-signal intensity on T1 weighted images that was markedly enhanced and heterogeneous signal intensity on T2 weighted images. Lack of contrast enhancement is a typical finding in benign epidermoid, although rim enhancement has been described in a few cases. In our patient, the contrast enhancement on CT scan in the otherwise typical epidermoid cyst suggested malignant degeneration. Using MR imaging, we could distinguish malignant epidermoid from benign epidermoid cyst more precisely.