Infrared thermography (IRT), or thermal imaging has long been proposed as a novel method in early detection of breast cancer. Most of the work done was through the detection of abnormal hotspot, or asymmetries in a thermal texture map. However, the surface temperature may not appear symmetric even for a healthy breast because of variations in blood supply and individual differences. In this paper, a method that is independent of the aforementioned symmetry is proposed. The breast under detection is initially excited by a group of patch antennas. Because of the differences in electromagnetic and thermal properties, the temperature increase will be different for healthy and abnormal tissues. Through the analysis of the temperature changing behavior, comparison of the temperature under each antenna with its vicinity point is done to determine whether cancerous tissue is present or not and further to detect its approximate location. A three-dimensional (3-D) finite-element method (FEM) has been used to simulate the thermal behavior of breast tissue exposed to antenna excitations.