Pathobiology of breast cancer--treatment implications.

In most patients (approximately 85%), breast cancer at the time of diagnosis is already a systemic disease. Multicentricity (20-40%) and synchronous (5-10%) and metachronous (15-30%) bilaterality are indicative of etiologically similar noxae. Ductal and lobular carcinoma in situ become invasive in approximately 50% of patients. Whereas ductal carcinoma in situ is mainly diagnosed clinically (lumpiness, tissue irregularity), lobular carcinoma in situ, a small, nonpalpable lesion, is usually discovered accidentally following biopsy for fibrocystic disease and/or suspicious mammography. Treatment of in situ and minimal (small invasive) breast cancer (less than or equal to 5 mm in diameter) is controversial, ranging from observation (lobular carcinoma in situ) over segmental excision to simple or radical mastectomy with or without lymphadenectomy and contralateral "mirror-image" biopsies. Long-term survival rates (90-95%) appear similar for patients with treated or untreated lobular carcinoma in situ. Patients with minimal breast cancer have as good a prognosis as those with ductal carcinoma in situ (long-term survival, 80-90%). Presently, a trend from radical to conservative surgery (lumpectomy, segmentectomy) is observed. Especially for in situ carcinoma, modified radical or even simple mastectomy may be considered overtreatment. For invasive carcinomas, lumpectomy and radiotherapy provide as good a chance of survival as radical mastectomy. Such equal survival indicates that although in 25% to 45% of patients with invasive carcinoma multifocal disease (in situ and invasive carcinoma) is left behind, subsequent radiotherapy is effective. Accordingly, patients with carcinoma in situ may be spared mutilating surgery in favor of radiotherapy. Because many patients at extraordinarily high risk of breast cancer cannot accept prophylactic mastectomy, thorough follow-up by clinical examination, mammography, sonography and biopsy is essential.