In this paper, four wearable UWB antennas are designed to detect and locate tumor cells placed within a heterogeneous phantom at different positions. The proposed antenna is operated within the 4.90 GHz to 15.97 GHz bandwidth range. It is fabricated, measured, and nearly matched between measured and simulated results. A cavity is formulated to back each antenna within the proposed detection system for increasing penetration and gain of propagated electromagnetic waves of the antenna design. The S-parameter of the proposed system was used to detect and locate a small tumor. The SAR results show that the absorbed power by the breast phantom tissues satisfies the IEEE standards which confirms the appropriateness of the proposed antennas for breast cancer early detection and localization system.