Breast-conserving surgery for invasive cancer: a principle based on segmental anatomy.

As the incidence of breast cancer increases in Japan, breast-conserving surgery becomes an important issue in the light of quality of life. We have demonstrated by 3-D reconstruction studies that ductal carcinoma in situ (DCIS) originates from the terminal duct-lobular unit (TDLU). Normal mammary epithelium anatomically located in the TDLU was shown to be biologically associated with cancerous change, particularly in specimens from patients who subsequently developed invasive carcinoma. Atypical ductal hyperplasia as well as DCIS expressed breast cancer associated antigen, providing further biological evidence that the atypical lesion at the TDLU are premalignant. Intraductal spread of carcinoma was defined as "DCIS was present clearly extending beyond the TDLU, or present prominently within the large ducts," and was classified into 3 grades according to the distribution of carcinoma in the duct-lobular system. We have developed a breast-conserving surgery consisting of quadrantectomy and regional lymph node dissection and immediate volume replacement using lateral tissue-flap (LTF). The quadrantectomy was employed on the basis of segmental anatomy of the duct-lobular system in which breast carcinoma originates. Fairly good cosmetic outcome as well as local control were obtained in the patients who underwent the immediate volume replacement using LTF. It must be emphasized that the quadrantectomy is a radical procedure in the sense that it aims at removal of all the carcinoma cells of the primary tumor.