The impact of lobular carcinoma in situ in association with invasive breast cancer on the rate of local recurrence in patients with early-stage breast cancer treated with breast-conserving therapy.

Purpose: The significance of lobular carcinoma in situ (LCIS) associated with invasive breast cancer in patients undergoing breast-conserving therapy (BCT) remains controversial. We examined the impact of the presence and extent of LCIS associated with invasive breast cancer on clinical outcome in BCT patients.
Methods and Materials: From 1980 to 1996, 607 cases of invasive breast cancer were treated with BCT. All slides were reviewed by a single pathologist. Positive margin was defined as presence of invasive carcinoma/ductal carcinoma in situ at the inked margin. Multiple clinical, pathologic, and treatment-related variables were analyzed for their association with ipsilateral breast tumor recurrence (IBTR) and true recurrence/marginal miss (TR/MM). Median follow-up was 8.7 years.
Results: Fifty-six patients (9%) had LCIS in association with invasive cancer. On univariate analysis, positive final margin, positive/no reexcision, smaller maximum specimen dimension, and the presence of LCIS predicted for IBTR. The 10-year IBTR rate was 14% for cases with LCIS vs. 7% without LCIS (p=0.04). On multivariate analysis, positive margin (p<0.01), positive/no reexcision (p=0.04), and presence of LCIS (p=0.02) remained independently associated with IBTR; positive margin (p<0.01) and LCIS (p=0.04) were also associated with TR/MM failure. When examining only cases with negative final margins, the presence of LCIS remained associated with higher IBTR and TR/MM rates (p<0.01).
Conclusion: The presence of LCIS was independently associated with higher rate of IBTR and TR/MM after BCT for invasive breast cancer. LCIS may have significant premalignant potential and progress to an invasive IBTR at the site of index lesion. The adequacy of excision of LCIS associated with invasive carcinoma should be considered in patients undergoing BCT.