Cancer cells marker?

[PECHAN at HELIX.MGH.HARVARD.EDU]

Hi netters:
   Does anybody know if exist some specific marker for tumor cells. I mean
something like GFAP-protein, which is only expressed in astrocyte cells.
My field is neurobiology, so I would be interested in glioma markers, but
the possible markers for another tumor cells would be also intersting for
me.
For any suggestions and messages I will be very thankful.

                  Best regards
                                                Peter Pechan
                                                Neurogenetics, MGH
                                                Boston, MA
                                        Pechan at HELIX.MGH.HARVARD.EDU