Adenocarcinoma cells trapped on a millipore filter in a patient with meningeal carcinomatosis.

A patient with meningeal carcinomatosis and hydrocephalus secondary to metastatic adenocarcinoma of the breast is presented. A ventriculoperitoneal shunt with a 3-microns Millipore filter was placed to prevent abdominal seeding of tumor cells. Within 5 days the shunt became plugged, requiring removal of the plugged filter. Tumor cells and hematogenous cells were found on the ventricular surface of the filter. The histological findings and the electron microscopy of these cells are presented. Millipore filters should probably not be placed in patients with carcinomatous meningitis.