– Ductal carcinomas account for 75% of all breast cancer; lobular and nipple carcinomas account for most of the remaining 25%.
Causes and Incidence
The cause of breast cancer is unknown, and 70% of women diagnosed with the disorder show none of the known risk factors, which include familial history; early menarche or late menopause; nulliparity or first child born after age 30; exposure to ionizing radiation; personal history of cancer or atypical hyperplasia; high-fat diet; and excessive alcohol consumption.
Breast cancer is the most common cancer among women in the United States, with more than 182,000 new cases diagnosed each year. The incidence is twice as high for women over 65 years of age as for those in the 45 to 64 age group. The incidence is rising, particularly among black women; however, the mortality rate has remained fairly stable.
Ductal carcinomas originate in the lactiferous ducts, where the cancer cells form a dense fibrotic core with radiating tentacles that invade surrounding breast tissue. The tumor mass is generally solid, nonmobile, irregularly shaped, poorly defined, and unilateral. Lobular carcinomas originate in the breast lobules and are bilateral. Nipple carcinomas originate in the nipple complex and often occur in conjunction with invasive ductal carcinomas. The lungs, bones, brain, and liver are common sites of breast cancer metastasis.
The most common presenting sign is a lump in the breast. About 50% are found in the upper outer quadrant. Nipple discharge may be present. Pain, tenderness, changes in breast shape, dimpling, and nipple retraction rarely occur until the disease reaches an advanced stage.
The prognosis dims markedly as the number of involved lymph nodes increases. Pleural effusion, ascites, pathologic fracture, and spinal compression can occur with advanced disease.
A mass detected by breast self-examination, physical examination, or mammogram needs further follow-up. Definitive diagnosis is made by incisional, excisional, or needle biopsy of the mass.
Treatment of choice is resection of the lump with removal of a varying amount of surrounding healthy tissue, ranging from a margin of breast tissue to the entire breast, axillary lymph nodes, mammary lymphatic chain, and pectoral muscles; breast reconstruction.
Adjunct systemic multidrug chemotherapy used primarily for premenopausal node-positive women; adjunct hormone therapy used primarily for postmenopausal nodeor receptor-positive women.
Radiation used as adjunct after surgery and for palliation in advanced disease; counseling for altered body image; recovery support groups; instruction in breast self-examination.