FACTORS INFLUENCING THE ESTIMATES OF PROLIFERATIVE LABELING INDEXES IN RECTAL-CANCER

Purpose. A detailed analysis was undertaken of some of the factors inf luencing the estimate of the labelling index (LI). Materials and metho ds: Thirty-three human rectal carcinomas were studied for their prolif erative activity as measured by the fraction of cells labelled with a single injection of IdUrd 1-8 h before surgical resection. Adjacent sp ecimens were stained both for histological examination and for flow cy tometry (FCM) assessment of labelled nuclei. Results: Two major differ ences were found. The superficial parts of each tumour almost always h ad significantly higher LI values than the deep part (34 versus 21%), yielding an average LI of 27%. The flow cytometry average value was mu ch lower (17%). This was partly due to the influence of diploid tumour s. There was a marked heterogeneity in the values, both within tumours , between tumours and between techniques. The average LI for the whole group differs by a factor of three, depending on the method of assess ment. Conclusions: All these values indicate a varying but rapid proli ferative turnover of cells, surprisingly being more marked in the supe rficial region, i.e. the opposite from the proliferation pattern of th e normal rectal mucosa. A biopsy, if taken from the superficial part o f the tumour, would therefore be biased toward higher values. This has implications for biopsy sampling for cell kinetic analysis. Histologi cal assessment avoids the contaminating effect of stromal cells, allow s architectural arrangements to be detected and is presumably a more r ealistic representation of proliferative activity. (C) 1998 Elsevier S cience Ireland Ltd.