Meningeal carcinomatosis from a clinically undiagnosed signet-ring cell primary in the gallbladder.

A patient with meningeal carcinomatosis is reported in whom the primary--which was not discovered clinically despite extensive investigation and cytological examination--proved to be the rare signet-ring cell tumor of the gallbladder. Determination of the nature and site of origin of the neoplastic cells in cytospin preparations of cerebrospinal fluid was complicated by the failure of conventional methods to stain cytoplasmic mucin. It is hoped that the application of monoclonal antibodies may resolve similar diagnostic problems in the future.