This volume summarizes the proceedings of the fifth biennial Cancer Teaching Symposium held on March 4 and 5, 1972 at the University of Chicago Pritzker School of Medicine. The program was prepared by Drs. MELVIN GRIEM, ELWOOD JENSEN, HAROLD SUTTON, JOHN ULTMANN, and ROBERT WISSLER. The purpose of the symposium was to present the current status of the challenging cancer problem, breast carcinoma, to the staff and students of this medical center and to students and in terested physicians from other institutions in the Chicago area. In a fashion similar to the other teaching symposia held in 1964, 1966, 1968, . and 1970, this symposium attracted over 450 physicians and scientists. In the course of one and one half days the audience had the opportunity to listen to 18 invited speakers and to the lively discussions. The formal presentations are recorded in these pages. This teaching symposium could not have been undertaken without the faithful assistance of the program committee, the cancer training grant education committee, the staff who recorded and transcribed the proceedings, and the editorial assistants. We wish to thank the following for their efforts: JULIE KANT, Administrative Secre tary for the Clinical Cancer Training Grant, as well as Dr. JAMES MARKS, MARGARET WOEHRLE, FRIEDA RANNEY, and ROSIE BARTLETT. This symposium received financial support from USPHS Clinical Cancer Train ing Grant 5T12 CA-08077-06 and from the Chicago Tumor Institute. MELVIN L. GRIEM, M. D. ROBERT W. WISSLER, Ph. D., M. D."

The methods of molecular biology, biochemistry, immunocytochem istry, and in-situ hybridization introduce new opportunities for the classification and functional characterization of cell receptors under normal conditions and for a better understanding of pathogenetic mechanisms in human diseases. The cellular localization and trans location of receptor proteins can be identified using morphological methods, and it is apparent that receptors and receptor defects play an important role in pathology, notably in genetic diseases, endocrine disorders, atherosclerosis, infections, and cancer. In this volume in ternational experts give a current review of the morphology and pathological aspects of cell receptors. The complex communication of multicellular organisms is coordi nated by two regulatory systems: neural and humoral. Both systems function via signaling substances (ligands) and signal-recognizing and -transmitting molecules, called receptors. The historical develop ment of the receptor concept is based upon Paul Ehrlich's theory of "receptors in the immune system," Langley's "receptive substances in postssynaptic membranes," and Earl Sutherland's discovery of "sec ond messengers" (cAMP and Ca2])."