Surgery for Classic, Pleomorphic and Non-classic Lobular Carcinoma In Situ: Surgery Rate, Risk of Upstaging and Short-Term Follow-Up

Background: The Dutch breast cancer guideline recommends surveillance for classic lobular carcinoma in situ (LCIS), unless there is a discrepancy with mammographic findings, and surgery for pleomorphic and non-classic LCIS. Objective: The aim of this study was to assess adherence to the guideline in daily practice, as well as the surgery rate, risk of upstaging, and events during follow-up. Methods: Selection of patients from a nationwide cohort diagnosed between 2011 and 2020. Patients with a history of in situ or invasive breast cancer or concomitant atypical ductal hyperplasia were excluded. Analyses comprised univariable analysis. Results: Of 1178 diagnoses, 1018 (86%) were classic LCIS, 129 (11%) were pleomorphic LCIS, and 31 (3%) were non-classic (florid or unspecified non-classic) LCIS. Surgery was performed in 323 patients. The surgery rate for classic LCIS was 19%, 83% for pleomorphic LCIS, and 84% for non-classic LCIS. The upstage rate for both classic and pleomorphic LCIS was 32%, and 31% for non-classic LCIS. LCIS was upstaged in 103 patients (32%); 24 (7%) to DCIS and 79 (25%) to invasive breast cancer. Follow-up of the 859 non-operated patients showed fewer than 4% with ipsilateral DCIS or invasive breast cancer. Conclusion: The surgery rates for classic, pleomorphic, and non-classic LCIS indicate that the guideline is well adhered to in daily practice. Given the high upstage rates and low number of subsequent DCIS and invasive breast cancer events in patients with classic LCIS, these patients appear to be well-selected for surgery versus surveillance. The results support the recommendation to operate on patients with pleomorphic/non-classic LCIS.