Breast Cancer

Abstract

Breast cancer is our fourth and final clinical example of the principles of molecular oncology. In the previous chapters on leukemia/lymphoma, colon cancer, and squamous cell carcinoma of the cervix, we saw several common threads. Tumors develop as the result of a germline or somatic mutation in a tumor suppressor gene or oncogene. Invasive cancer is the endpoint of a multiple-step evolution that can be tracked as a series of progressive histologic and molecular lesions. Breast cancer demonstrates these common principles, but the details are less clearly understood. What percent of cases is due to inherited risk (germline mutation) versus sporadic breast cancers (somatic mutation)? At the moment, we can estimate the inherited risk as 5% of breast cancers. But this estimate is likely to change as we discover more of the genes involved. What are the steps in evolution? Under the microscope we recognize the progression of hyperplasia, atypical hyperplasia, in situ carcinoma, and invasive cancer. The molecular evolution of breast cancer is less clearly understood. The linear sequence of molecular events that we saw in Figures 8.1 and 9.1 for colon and cervical cancer may not exist in as simple a form for breast cancer.