Abstract: A microwave antenna for use in a system for detecting an incipient tumor in living tissue such as that of a human breast in accordance with differences in relative dielectric characteristics. In the system a generator produces a non-ionizing electromagnetic input wave of preselected frequency, usually exceeding three gigahertz, and that input wave is used to irradiate a discrete volume in the living tissue with a non-ionizing electromagnetic wave. The illumination location is shifted in a predetermined scanning pattern. Scattered signal returns from the living tissue are collected and processed to segregate skin tissue scatter and to develop a segregated backscatter or return wave signal; that segregated signal, in turn, is employed to detect any anomaly indicative of the presence of a tumor or other abnormality in the scanned living tissue.