Breast-conserving surgery for pure non-classic lobular carcinoma in situ: A single institution's experience.

Background: Non-classic lobular carcinoma in situ (NC-LCIS) is a rare pre-cancer breast lesion that warrants excision to exclude invasive disease. In patients pursuing breast-conserving surgery (BCS) for NC-LCIS, the need for wide surgical margins is controversial. We characterized the outcomes of women diagnosed with NC-LCIS at a large, academic medical center.

Methods: Female patients seen at our institution from 2008 to 2018 with pure NC-LCIS were retrospectively identified. Patients were excluded if NC-LCIS was diagnosed in the background of invasive cancer or ductal carcinoma in situ. Clinicopathologic and follow-up data were collected. Rates of upstage, re-excision, and recurrence were calculated.

Results: We identified 26 patients with pure NC-LCIS diagnosed on biopsy. 80.8% of patients initially pursued breast conservation, while 19.2% underwent mastectomy. At definitive surgery, 11.5% were upstaged. Among 19 non-upstaged patients that underwent BCS, 47.4% had at least one re-excision and 26.3% converted to mastectomy. In patients receiving BCS without completion mastectomy, 64.3% had final surgical margins that were negative for NC-LCIS, while 35.7% had positive or close margins. No recurrences in patients with negative margins were observed. One patient with positive margins developed a recurrence 8.3 years post-surgery, and one patient with close margins did 2.2 years post-surgery. All non-upstaged patients were alive at time of analysis with no evidence of invasive disease.

Conclusion: We presented the outcomes of one of the largest series of pure NC-LCIS. In patients with NC-LCIS pursuing breast conservation, re-excisions and completion mastectomies were common. However, when negative margins were achieved, prognosis was excellent.