Abstract P1-01-10: Pleomorphic lobular carcinoma in situ (PLCIS)-presentation, associated lesions and outcome

Abstract

Abstract Pleomorphic lobular carcinoma in situ (PLCIS) is an uncommon lesion characterised by dyscohesive lobular cells showing high grade nuclei. It is commonly associated with comedo necrosis and luminal calcifications and hence diagnosed on mammographic screening. Data on the presentation, focality, associated lesions, optimal treatment and outcome of PLCIS is patchy. Methods Cases diagnosed as PLCIS between 2005 and 2015 were identified from the imaging and pathology databases of two UK large breast screening units. Cases diagnosed on diagnostic core biopsy/VAB or surgical excisions were included. Comprehensive data was collected on age, mode of presentation (screening vs symptomatic), imaging (mammography, ultrasound and MRI), surgical management, histological features on core biopsy and excision including type, grade and immunohistochemical profile of associated ductal carcinoma in situ (DCIS) and invasive carcinoma. Results 86 cases with the diagnosis of PLCIS (confirmed by review and e-cadherin negativity) were identified. The mean patient age at diagnosis was 61.04 years, range: 39-84 years. 32 cases were treated with wide local excision with/without axillary procedure. A total of 38 patients were screen detected & 36 cases were diagnosed in the symptomatic setting. Others presented as incidental calcifications on family history screening, incidental histological findings in breast reductions and risk reducing mastectomy. On mammography, 6 patients presented with an asymmetrical density, with or without calcifications, 25 with calcifications, 44 as a mass and 2 as stromal deformity. No mammographic abnormality was found in 9 cases. PLCIS was multifocal in 19.7% of cases, diffuse in 9.9%, focal in 69% and multi-centric in 1.4% on imaging. Histologically, PLCIS was the most advanced lesion on core biopsy without associated DCIS or invasive disease (pure PLCIS) in 23 patients. Of these, surgical excision revealed an invasive carcinoma in 7 cases (upgrade rate =30.4%). Six more patients presented as DCIS and PLCIS on core biopsy; three of whom (50%) had invasive disease on excision. Classical LCIS was associated with PLCIS in 27/86 cases (31.3%). The most common type of associated invasive carcinoma on surgical excision was invasive classical lobular carcinoma (ILC, 40 cases), followed by invasive pleomorphic lobular carcinoma (IPLC, 27 cases). Ductal no special type carcinoma, solid papillary and tubulo-lobular carcinoma were also identified. The size of PLCIS on excision ranged from 1-80mm. DCIS was associated in 26.7% of cases. The majority of invasive cancers were of grade 2 (53.5%) and 3 (19%). The tumors were ER positive (53 cases), PR positive (43 cases) and HER2 negative (52 cases). Conclusion PLCIS is an uncommon in situ carcinoma presenting via mammographic and also in the symptomatic setting. Unlike classical LCIS, PLCIS is a disease of postmenopausal women. It is multifocal in approximately one fifth of the cases. PLCIS is commonly associated with classical LCIS and both ILC and IPLC. When identified in core biopsy, the upgrade rate in this series was 30.4% which increased to 50% if the lesion co-existed with DCIS. The associated cancers are often ER positive, HER2 negative. These findings support managing those lesions surgically as per DCIS. Citation Format: Shaaban AM, Smith S, Bradley S, McMahon M, Sharma N. Pleomorphic lobular carcinoma in situ (PLCIS)-presentation, associated lesions and outcome. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-01-10.