Invasive Pleomorphic Lobular Carcinoma of the breast: Clinicopathological features, treatment patterns and outcomes

Introduction: Pleomorphic lobular carcinoma (PLC) is a rare variant of invasive lobular carcinoma of the breast (ILC) and few studies have reported controversial data regarding its outcomes. The information provided appears to indicate that PLC is more aggressive and has worse outcome when compared to classical ILC (cILC); however, due to its rarity, studies with a considerable cohort of patients are lacking. The purpose of this study was to compare the clinicopathological characteristics and disease outcomes of PLC patients to those with cILC in a large cohort from a single institution. Methods: A retrospective comparative study was performed, including 226 patients with PLC and 2067 patients with cILC operated at the European Institute of Oncology (EIO) between 2001 and 2018. The median follow-up period for both groups was 7 years. Results: 5- and 10-years invasive disease-free survival were better in the matched classical lobular carcinoma patients compared to the pleomorphic variant. The 5- and 10-years overall survival confirmed the trend previously seen in favor of the classical variant, with a 5-year survival of 98.4% vs 83.6% and a 10-year survival of 93.4% vs 69.5%, respectively. Conclusions: The pleomorphic variant has been confirmed to be characterized by worse clinicopathological characteristics and worse clinical outcomes than the classical variant.