Background: Bilateral/contralateral prophylactic mastectomy (PM) is offered to high-risk women to decrease their actual or perceived breast cancer risk. When an invasive occult cancer is identified, prevailing wisdom suggests that an axillary dissection be performed. This single-institution study aims to identify patients who may benefit from sentinel node biopsy (SLNB) at the time of prophylactic mastectomy.
Study design: We performed a retrospective review of a prospective database of patients treated at our institution with bilateral/contralateral PM between 1995 and 2006. We examined patients' clinicopathologic characteristics in comparison with their incidence of occult cancer in the contralateral breast or axilla.
Results: There were 449 patients who underwent PM and SLNB. Twenty-eight underwent bilateral PM. Of the 28, no occult cancers were identified. Occult cancers were identified in 18 of 420 (4.3%) contralateral prophylactic specimens; they were invasive in 6 (1.4%). In cases of occult carcinoma, the primary established tumor was more likely to be of invasive lobular histology. Eight of 420 (2%) patients had a positive contralateral sentinel node, and within this subset of 8 patients the majority had locally advanced disease on the known tumor side. Other features associated with a positive contralateral sentinel node included the presence of lymphovascular involvement or skin or nipple involvement and grade 2 to 3 invasive primary established tumors.
Conclusions: Overall, SLNB in patients undergoing bilateral PM or contralateral PM associated with early-stage disease is not indicated. But patients with locally advanced primary breast cancers have a significantly increased risk of occult cancer in the contralateral axilla, likely due to crossover metastasis; this select group of patients may benefit from SLNB at the time of surgery.