The term lobular carcinomain situ (LCIS) is misleading. This lesion is more appropriately termed lobular neoplasia. Strictly speaking, it is not known to be a premalignant lesion, but rather a marker that identifies women at an increased risk for subsequent development of invasive breast cancer. This risk remains elevated even beyond 2 decades, and most of the subsequent cancers are ductal rather than lobular. LCIS is usually multicentric and is frequently bilateral. In a large prospective series from the National Surgical Adjuvant Breast and Bowel Project with a 5-year follow-up of 182 women with LCIS managed with excisional biopsy alone, only eight women developed ipsilateral breast tumors (four of the tumors were invasive). In addition, three women developed contralateral breast tumors (two of the tumors were invasive).
Most women with LCIS have disease that can be managed without additional local therapy after biopsy. No evidence is available that re-excision to obtain clear margins is required. The use of tamoxifen has decreased the risk of developing breast cancer in women with LCIS and should be considered in the routine management of these women. The NSABP-P-1 trial of 13,388 high-risk women comparing tamoxifen to placebo demonstrated an overall 49% decrease in invasive breast cancer, with a mean follow-up of 47.7 months. Risk was reduced by 56% in the subset of 826 women with a history of LCIS, and the average annual hazard rate for invasive cancer fell from 12.99 per 1,000 women to 5.69 per 1,000 women. In women older than 50 years, this benefit was accompanied by an annual incidence of 1 to 2 per 1,000 women of endometrial cancer and thrombotic events. (Refer to the PDQ summary on Breast Cancer Prevention for more information.)
Bilateral prophylactic mastectomy is sometimes considered an alternative approach for women at high risk for breast cancer. Many breast surgeons, however, now consider this to be an overly aggressive approach. Axillary lymph node dissection is not necessary in the management of LCIS.