The modified round block technique (MRBT) is a level I oncoplastic breast-conserving surgery (OBCS), which contains a very wide glandular flap created by extensive dual-plane undermining that is achieved by entire subcutaneous dissection and approximately 50% dissection of the breast parenchyma from the pectoralis muscle. A retrospective analysis was performed for 100 patients who underwent OBCS using MRBT from February 2009 to October 2017. The incidence of positive margin was 7.0% (seven cases), and there has been no local recurrence during a median follow-up period of 68 months. Short- and long-term complications included fat necrosis (11.0%), infection (4.0%), and hematoma formation (4.0%). When patients were divided into two groups based upon the preoperative mammography findings, fat necrosis occurred in 5.2% of the patients with extremely dense or heterogeneously dense mammography, and in 19.0% of patients with scattered fibroglandular or entire fat mammography, which showed a statistically significant difference. Therefore, in level I OBCS, the extent of dual-plane undermining should be minimized to less than 50% of the total parenchyma in fatty breasts.
Keywords: Breast-conserving surgery; Fat necrosis; Modified round block technique; Oncoplastic surgery.