Studies on the distribution of abnormal cells in cytologic preparations. V. The gradient of cell deposition on slides.

A model system of exfoliated normal human cervicovaginal squamous cells, exfoliated rodent tumor cells, and acellular, viscous, mucus-like material was used to investigate the gradient of cell deposition on smear preparations. Smears were made from left to right with parallel strokes, without overlapping smearing and without rotating the instrument of cell collection. With this technique a gradual decrease in the total number of cells was recorded along the pathway of the smear. The proportion of tumor cells, however, increased halfway along the smearing pathway. The midway increase was significant for wooden spatulas or cotton swab applicators but less marked for plastic spatulas. It would appear that normal squamous cervicovaginal cells, because of their large flat surface, attach readily to the flat surface of the slide and become "consumed" from the material carried by the instrument. On the other hand, the relatively smaller round tumor cells are "pushed" forward by the instrument during the smearing procedure. These considerations may be of significance in screening programs for tumor cell detection.