Rapid estimation of the proliferating index of brain tumours.

A rapid and versatile method has been developed for estimating proliferating/labelling indices (enumerated S-phase cells) of brain tumours. Fragments of fresh, surgically excised tumour specimens are labelled in vitro with 10 microM bromodeoxyuridine (BrdU) at 37 degrees for 1 hour in MEM + 10% FCS, washed in PBS, blotted dry and then imprinted on glass slides leaving a mirror image monolayer of cells of the impressed surface. The incorporated BrdU is then detected indirectly by immunoperoxidase staining after fixation. No fewer than 1000 cells are counted under high power and the PI is expressed as the % of BrdU positive cells to the total number counted. The PI of the various tumours analysed ranged 2.54-13.08% for gliomas, 5.29-7.60% for metastases, 0-0.83% for benign meningiomas. Thirty one cases have been studied. Results, obtainable within a few hours of tumour biopsy/resection, correlate favourably with published flow-cytometry proliferating indices for the tumours analysed and thus validate the method as a comparable alternative to in vivo BrdU labelling.