The microwave system is employed for the detection of cancerous tumors and is particularly effective in the early detection of such tumors. The system is of the dual type, combining in a single unit a passive radiometer with an active microwave transmitter. The sensitive passive microwave radiometer is adapted to sense subsurface temperatures, coupled with a solid state microwave transmitter for providing localized heating of the subsurface tissue, thereby taking advantage of the differential heating due to vascular insufficiency associated with the thermal characteristics of tumors, thus highlighting and enhancing early detection of cancer. A delay period on the order of five minutes is defined between heat application and detection in order to optimize temperature differential. The transmitter or applicator is for internal use employing a radiating element adapted for use with an endoscopic apparatus.