Pleomorphic and Florid Lobular Carcinoma In Situ Variants of the Breast: A Clinicopathologic Study of 85 Cases With and Without Invasive Carcinoma From a Single Academic Center.

The natural history and optimal treatment of pleomorphic (PLCIS) and florid (FLCIS) lobular carcinoma in situ variants remains uncertain. We reviewed the clinicopathologic features and management of LCIS variants at our institution over a 20-year period. Of 85 cases (61 PLCIS, 24 FLCIS), 77% were associated with invasive carcinoma (84% lobular, 13% ductal/lobular, 3% ductal) and only 17% (9 PLCIS, 5 FLCIS) were pure. Most (81%) invasive carcinomas were grade 2, with all grade 3/pleomorphic invasive lobular carcinomas (ILC) associated with PLCIS, and all grade 1 tumors associated with FLCIS. PLCIS-associated invasive carcinomas were more often ER- (21%) or HER2+ (14%) than FLCIS-associated tumors (100% ER+, 6% HER2+). LCIS variants were unifocal and co-localized with invasive carcinoma in 20/20 selected spatially mapped cases, whereas classic LCIS (CLCIS) was multifocal with wider distribution (10/17). Of 21 pure LCIS variants on core biopsy, all represented the radiographic (95%) or palpable (5%) target. The excisional upgrade rate was similar for PLCIS (38%) and FLCIS (33%). Pure LCIS variants on core biopsy were often (20%) HER2+ and had a higher Ki-67-index than synchronous CLCIS (P=0.002). Lower ER expression in LCIS variants versus CLCIS was due to ER- apocrine PLCIS. ER and HER2 were consistently concordant between LCIS variants and upgraded ILC but discordant between synchronous CLCIS and LCIS variants in 5/14 (36%). Pure LCIS variants were excised to negative margins and frequently (58%) treated with endocrine but not radiation therapy without recurrences. In summary, PLCIS and FLCIS demonstrate features of direct precursor lesions warranting surgical excision.