BACKGROUND : Upstaging from DCIS to invasive ductal carcinoma varies widely from 0 to 59%. We aim to identify risk factors associated with upstaging in all DCIS patients and based on specific surgical intervention. METHODS : Patients with a pre-operative diagnosis of DCIS undergoing BCT or mastectomy were reviewed. Multivariable analysis was performed to identify risk factors for upstaging. RESULTS : In total, 623 patients had a preoperative diagnosis of DCIS. Upstaging occurred in 74 patients (12%) overall. There was no difference in upstaging rates between mastectomy and BCT (11% v 14% p = 0.27). Sentinel lymph node biopsy was positive in 4/212 patients (1%). Multivariable analysis revealed suspicion of microinvasion (OR 5.7 95%CI2.2-14.9), surgeon suspicion of invasive disease (OR 2.7, 95% CI 1.2-6.4) and larger size/multicentric/extensive tumor (OR 1.9 95% CI 1.1-3.4) increase risk of upstaging. CONCLUSIONS : Suspicion of microinvasion, surgeon suspicion, and tumor size can be used to help guide the use of sentinel lymph node biopsy. For patients without these high risk characteristics, it is hard to justify the use of concurrent SLN biopsy for patients who undergo BCT.