Cystic lesions of the pineal region - MRI and pathology

Pineal lesions are rare. Tumours in this location comprise 0.4-1% of intrac ranial tumours. They grow mainly as solid-mass lesions, and cystic tumours are not common. On MRI, a cystic configuration is associated usually with n on-neoplastic pineal lesions rather than with a tumour, but analysis does n ot allow cystic pineal tumours to be distinguished from glial cysts with ce rtainty. We compared neuroradiological and pathological data from 13 cystic pineal lesions, analysing preoperative MRI. Formalin-fixed, paraffin-embed ded surgical specimens were stained routinely and immunocytochemically, usi ng the streptavidin-biotin-complex method. Histology revealed six pineocyto mas, four glial cysts, an arachnoid cyst, a low-grade astrocytoma and a ter atoma. Signal characteristics of pineocytomas were similar in many respects to those of glial pineal cysts. Histomorphological analysis allowed unambi guous discrimination between pineocytomas and glial pineal cysts.