For early-stage tumor detection, microwave imaging is a widely appreciated modality as of now. Development of an efficient microstrip patch antenna with reduced cost and complexity is still a challenging task that must be addressed. In this work, we suggest a low-profile partial ground plane dual band rectangular patch antenna for identifying the presence of early-stage tumor in the muscular region of breast mass. The proposed antenna model is operating on two different frequency bands, i.e., 2.48 and 3.46 GHz. The model is simulated with a partial ground plane and modified feedline with specially designed defected radiating patch. It is optimized by considering the efficiency of the antenna by evaluating different parameters, such as: return loss (S11), radiation pattern, VSWR, and radiation efficiency. Further, the antenna model is experimented using a simulated four-layered breast phantom model with an early stage of muscular breast tumor in side. The detection of tumor is claimed based on the difference in observed antenna parameters compared to those in the absence of tumor inside the breast mass.