Fluorescent location of brain tumour cells in wax embedded sections.

Tumour cells and certain normal cells in wax embedded brain sections possess active isoenzymic forms of a cell surface protease. The normal isoenzymic forms are recognised by protease inhibitors present in normal serum; the tumour isoenzyme remains active after exposure to serum. Fluorescent location of cells possessing active isoenzyme after serum treatment reveals the tumour cells in these sections.