Quantitative tumor cytochemistry--G.H.A. Clowes Memorial Lecture.

Quantitative optical cytochemistry permits the determination of many different parameters in whole cells or parts of cells. Total amounts of DNA, RNA, and protein and/or the amounts of these substances in nucleus or nucleolus are examples. Techniques in this field have contributed considerably to the development of our present conceptions of normal cell growth and regulation. Normal cell study has, however, predominated so that tumor work has not yet been very extensive, even though quite eqrly on, in the 1940's, a conspicuous cytochemical peculiarity was found in cancers, namely, a pronounced variability between cells with regard to several measurable parameters. The result has been different kinds of technical difficulties, which are especially great in work on tumor material. However, as years passed, a fair amount of information was accumulated from studies of different parameters in tumors. Only a few years ago this experience clearly indicated that, provided very considerable improvements were made in technique, several cytochemical methods could be used as efficient supplements to morphological cytodiagnostic work, especially in such important clinical fields as preneoplasia identification, malignancy grading, and judgment of the state of growth of for instance, hormone-stimulated populations and also the distinction, so difficult in morphology, between "atypical hyperplasia" and "truly malignant" states. In an effort to eliminate the foremost of these technical difficulties, during the last few years we have developed a comprehensive system for large-scale uni- and multiparameter measurements aimed specifically at the types of specimens encountered in cytopathological work. The system is based on cytophotometry in ultraviolet and visible light, interferometry, and fluorometry and also encompasses special arrangements to simplify the identification and recovery of individual cells for different types of study. Instruments for facilitation of the comparison of cytochemical results with morphological findings are also included.