Final answer:
The patient with a mammogram showing primarily adipose tissue in the breast is most likely above 60 years, as older women have increased fat in their breasts due to decreased estrogen levels after menopause.
Step-by-step explanation:
When a baseline mammogram shows that a patient's breast consists primarily of adipose tissue, it indicates that the patient is most likely to be above age 60 years. This is because, as women age, particularly after menopause, they tend to have an increased proportion of fat in their breasts. The hormone estrogen, which is produced by the ovaries and promotes the development of glandular tissue in the breast, declines after menopause, leading to a relative increase in fatty tissue compared to dense breast tissue. This typically occurs at about 50 years of age, where women commence menopause and experience a reduction in estrogen, thereby increasing the fat content in their breasts.