Inflammatory pseudotumour of the central nervous system: clinicopathological study of one case and review of the literature.

A 58-year-old male who had been diagnosed as having polymyositis was found to have a mass in the fourth ventricle. This mass showed features of an inflammatory pseudotumour. This lesion has been described in many parts of the body including the central nervous system. This case showed some features different from the previously reported cases in the central nervous system (i.e. presence of necrosis and association with polymyositis) which may throw some light on the pathogenesis of the condition. Inflammatory pseudotumour is most likely to be caused by an exaggerated immunological process and is sometimes associated with high levels of serum immunoglobulin.