Introduction

Breast cancer remains the most common non-skin cancer diagnosed and the second leading cause of cancer death (lung cancer now leading) in US women each year. Breast cancer does occur in men but much less frequently, affecting about 1500 men per year. Due in large part to the increased use of mammographic screening and advances in adjuvant therapy, mortality rates from breast cancer have been slowly declining for the last 10 years. Early stage breast cancer is successfully treated in over 90% of patients. Currently only about 10% of patients present with metastatic breast cancer. Of patients with apparently localized disease, approximately one-quarter with lymph-node negative and one-half with lymph-node positive breast cancer will ultimately develop metastatic disease. This means that of the 180 000 women in the US diagnosed with breast cancer each year, the disease proves fatal in ∼40 000.

Ductal carcinomas account for about 85% of invasive breast cancers, lobular carcinomas about 10%. Other types of breast cancer including medullary, mucinous, tubular, and colloid are uncommon subtypes of ductal carcinomas with a slightly more favorable prognosis. Though there are some differences in the pattern of recurrence, ductal and lobular cancers are treated similarly. Sarcomas, metaplastic carcinomas, neuroendocrine tumors, and other rare histologic types are treated quite differently and will not be discussed further.

Pattern of spread and recurrence

Breast cancer can spread through either the lymphatic system to the axillary (or less commonly internal mammary) lymph nodes or hematogenously to distant organs.