Among various types of cancer, breast cancer is considered to be the most common that affects thousands of women all over the world. Several imaging tools are being used for breast cancer detection and diagnosis. Mammography and B-mode ultrasound (US) are the primary screening tools for breast lesions. However, mammography is limited with low sensitivity especially in women with dense breasts, who appear to be at higher risk of breast cancer. Additionally, the B-mode US suffers from low specificity in the differential diagnosis of breast lesions. Therefore, it is clinically significant to develop screening techniques that could eliminate previous limitations. Photoacoustic (PA) has been showing potential for early stage detection and staging breast cancer due to its unique abilities to acquire functional and molecular information of the breast lesions. We have developed an optimized US and PA tomography system, which uses custom designed all reflective based optics to create an omnidirectional ring-shaped beam to illuminate a cross-section of the breast tissue and acquire thegenerated acoustic waves by using a full-ring US transducer. The developed PA tomography (PAT) system can potentially make a more uniform illumination of the breast tissue and more importantly enhance the imaging depth. In this study, development of the full-ring illumination and the results of our initial feasibility US/PA tests are presented.