Abstract P5-22-01: Evaluating the risk of upgrade to invasive breast cancer and/or DCIS on excision following a diagnosis of non-classic lobular carcinoma in situ

Abstract

Abstract Introduction: Non-classic lobular carcinoma in situ (NC-LCIS) is a rare pathologic entity which encompasses a variety of histologic diagnoses. As such its natural history, including upgrade rates to invasive cancer (IC) or ductal carcinoma in situ (DCIS) on excision, is poorly characterized. We sought to evaluate the risk of upgrade to IC or DCIS when NC-LCIS is diagnosed on core biopsy. Methods: After obtaining IRB approval, institutional pathology databases were searched for NC-LCIS core biopsy diagnoses (carcinoma in situ (CIS), carcinoma in situ with ductal and lobular features (CIS/DLF), pleomorphic LCIS (P-LCIS), variant LCIS (V-LCIS), LCIS with necrosis). Cases with a NC-LCIS core biopsy diagnosis and with available pathology results from subsequent surgery were included. Cases with known concurrent ipsilateral IC, DCIS and/or atypical ductal hyperplasia were excluded. Results: 107 cases with NC-LCIS in any pathology report were identified (1998-2016); 44 were excluded due to concurrent ipsilateral IC, the remaining 62 patients with 63 core biopsy diagnoses of NC-LCIS all underwent surgical excision and formed our study cohort. Median age was 56 years (range 43-83); 43 (68%) were postmenopausal. NC-LCIS was diagnosed on core biopsy for mammographic findings in 57 (90%) cases and for MRI findings in 6 (9%). All were BI-RADS 4 lesions; calcifications were the most common biopsy indication (50 (78%)). CIS/DLF was the most common term used for NC-LCIS (28 (44%)), followed by CIS (18 (29%)), V-LCIS (14 (22%)) and P-LCIS (3 (5%)). On core biopsy, 36/44 (82%) of NC-LCIS cases were E-cadherin negative, 38/41 (93%) were ER positive, and 6/34 (18%) were HER2 positive. IC and/or DCIS were diagnosed on subsequent surgery in 22 (33%) of patients, of which 14 (67%) were IC and 8 (18%) had DCIS only. LesionTotalE-cadherin negativeUpgraded, N (%)Invasive cancer, N (%)DCIS only, N (%)CIS188/10 (80%)3 (16%)2 (67%)1 (33%)CIS/DLF2819/23 (83%)12 (43%)7 (58%)5 (42%)P-LCIS31/1 (100%)3 (100%)2 (67%)1 (33%)V-LCIS148/10 (80%)4 (29%)3 (75%)1 (25%) Median IC size was 0.2 cm (0.06-1.1 cm). IC histology was ductal in n=4 (29%), lobular in n=7 (50%), and ductal and lobular in n=3 (21%). Among the 14 invasive lesions, 5 (36%) were grade I, 5 (36%) were grade II and 2(13%) were grade III, (grade was not reported for 2 remaining ICs); 12/14 (86%) were ER positive and 1/14 (7%) was HER2 positive; none had LVI or positive nodes. Among the 42 cases not upgraded, 13 (31%) had mastectomy, 9 (21%) had excision and radiation, 20 had excision only, all had negative margins. At median follow-up of 60 months (1-224 months), 1/20 patients treated with excision only was diagnosed with DCIS, 14 months after surgery for CIS/DLF on core biopsy. Conclusions: In this large series of NC-LCIS diagnosed on core biopsy, the upgrade rate to carcinoma was 33% supporting the recommendation for routine excision of these lesions. The cancers found at excision were all stage I and the majority were grade I or II. At a median follow-up of 60 months only 1/20 patients with pure NC-LCIS treated with excision alone developed a future ipsilateral cancer. Further study of the natural history of these rare lesions is warranted. Citation Format: Nakhlis F, Harrison BT, Lester SC, Hughes KS, Coopey SB, King TA. Evaluating the risk of upgrade to invasive breast cancer and/or DCIS on excision following a diagnosis of non-classic lobular carcinoma in situ [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-22-01.