Prognostic factors for residual occult disease in shave margins during partial mastectomy

Purpose Shave margins have been shown to decrease positive final margins in partial mastectomy. We investigated prognostic factors associated with residual disease in shave margins. Methods Patients with invasive breast carcinoma and ductal carcinoma in situ (DCIS) who had circumferential shave margins excised during lumpectomy were abstracted from a retrospective database from 2015 to 2018. We defined residual occult disease (ROD) as either (1) residual disease in a shave margin when the initial lumpectomy specimen had negative margins or (2) residual disease in a shave margin that did not correspond with the positive lumpectomy margin. We identified the frequency of ROD and conducted logistic regression analysis to identify associated prognostic factors. Results 166 Patients (139 invasive carcinoma, 27 DCIS) were included with median follow-up of 28 months (9–50 months). Residual occult disease existed in 34 (24.5%) with invasive carcinoma and 8 (29.6%) with DCIS. In univariate analyses of the invasive group, invasive lobular carcinoma and a positive initial, non-corresponding lumpectomy margin were predictive of ROD (OR 3.63, p = 0.04, OR 3.48, p = 0.003 respectively). In multivariate analysis, a positive lumpectomy margin remained significant, p = 0.007. No variables were associated with ROD in DCIS. Conclusion Residual occult disease was shown to be a frequent event in this analysis of lumpectomy with circumferential shave margins. Having a positive initial lumpectomy margin was predictive of ROD in a non-corresponding margin. Surgeons should consider not being selective in their shave margins or margin of re-excision if shave margins were not obtained in their initial surgery.