Upgrade rates and treatment recommendations for patients with pleomorphic and florid lobular carcinoma in situ.

e12563 Background: Long term follow up data is limited regarding the natural history of patients diagnosed with Pleomorphic Lobular Carcinoma in situ (PLCIS) and Florid Lobular Carcinoma in situ (FLCIS) and there is a lack of consensus on management recommendations for these high risk lesions. Methods: This retrospective, single institution study identified patients from our pathology database with PLCIS and FLCIS diagnosed after core needle biopsy or breast reductive surgery. Clinical, radiologic and pathologic findings were analyzed. Patients with concurrently diagnosed invasive cancer or DCIS were excluded. The immediate and delayed risk of developing invasive cancer was calculated. Results: All 45 patients were female. The median age was 61 and the majority of patients were peri- or post- menopausal 77% (35/45). Eleven patients (24.4%) had a history of breast cancer in the contralateral breast. Three patients had a genetic mutation (6.6%). Twenty-seven patients had a family history of breast cancer (60%). The most common targeted imaging findings were unifocal suspicious calcifications on screening mammogram 84.4% (38/45) in the absence of a mass lesion 86.7% (39/45). The histology on biopsy was PLCIS 75.6% (34/45), FLCIS 11.1% (5/45) and a combination of variant types 13% (6/45). Forty-four patients underwent surgery to include wide local excision in 84% (37/44) and mastectomy in 15.9 % (7/44). There was concordance with the paired biopsy and surgical resection specimens in 95% of cases (42/44). In two patients with FLCIS, only classic LCIS remained on excision. One patient had concurrent DCIS on excision (2.3%) Ten patients (22.7%) had diagnoses upgraded to invasive carcinoma on excision; the majority being T1a (70%) and the remainder T1b (30%). In 52% (23/44) of cases margins were reported negative for PLCIS and FLCIS with ≥ 2 mm distance from the targeted lesion after the initial surgery; 15.9% (7/44) margins were 1 mm to 1.9 mm; 15.9% (7/44) cases < 1 mm; 9.1% (4/44) with PLCIS at the inked margin. Close margin management included re-excision in 6, mastectomy in 2, radiotherapy after conservative therapy in 4 and observation in 4. Eighteen patients received adjuvant endocrine therapy (41%) for a mean of 24 months. There were 4 patients with PLCIS that developed ipsilateral recurrences in the same quadrant after imaging surveillance (9%); of which 2 were local, and two local regional, occurring 135 months, 106 months, 89 months, and 60 months after the initial diagnosis; the latter patient died of metastatic breast cancer 96 months after initial diagnosis. New cancers were estrogen receptor positive invasive lobular carcinomas and PLCIS. Three of these 4 patients had close margins. Conclusions: There is both an immediate (25%) and delayed (9%) risk of developing invasive breast cancer in patients with PLCIS and FLCIS. Our data supports excision of PLCIS to ≥ 2mm margins and maintenance of long term follow up.