Characteristics of breast cancer in an incident cancer population.

The effectiveness of film mammography is a source of concern to radiologists because neither the ribs nor retromammary space is included on the films in good quality examinations. One hundred seven incident cancers were detected in 10,034 self-referred women followed at the University of Michigan Breast Cancer Detection Demonstration Project (UM-BCDDP) for 5 years. These cancers were analyzed for location on the film, method of detection, size, histology, and the number of films required for detection. Mammography alone detected 52 (49%) of the cancers, whereas physical examination alone detected 15 (14%). The other 40 cancers were detectable on both examinations. All of the 92 cancers detected by mammography were visible in both the mediolateral and the craniocaudal views. Only 2.2% of these cancers were within 1 cm of the posterior edge of the film in the mediolateral view; 18.7% were within 1 cm of the posterior edge in the craniocaudal view. These incident cancers were smaller, and fewer were located within the posterior 1 cm of the breast than in a similar study using the UM-BCDDP prevalent cancer population. Mammography consistently detected cancer in the breast, regardless of tumor size, histologic type, or location within the breast.