Breast implants are placed either behind the breast tissue (subglandular position) or behind the breast tissue and the pectoralis major muscle (submuscular position). There are proponents for each technique, based on opinion and surgical training. Regardless of the placement of the implant, the fill material and the size, having breast implants does not interfere with breast self-examination, physician breast exams, mammograms, ultrasound, MRI or any other cancer detection techniques.
When having a mammogram, women should inform the mammography technician that they have breast implants in place. A "displacement" technique will be done to help push the breast tissue off the implant and to allow the X-ray beams to shoot through the breast to accurately visualize the tissue. Occasionally, additional views are taken when an implant is in place.
Mammograms are generally not recommended until age 40, as before this age breasts are quite dense and visualization is not reliable. A 40-year-old woman should have a mammogram as a baseline exam before considering any surgery of the breasts, including augmentation, reduction or a breast lift.
Two studies in the literature actually showed that women with breast implants had earlier detection of breast cancer than those without implants, perhaps because the implant served as a surface against which a lump was palpated (felt) during breast self-examination.
Having breast augmentation is a personal choice and should be researched in detail before you commit to any surgery. Make sure you consult with a plastic surgeon who is board-certified and experienced in the procedure you are seeking.