RESUMEN
PURPOSE: The purpose of this study was to identify the clinical and pathological factors that differentiate pleomorphic invasive lobular carcinoma (PILC) from classic invasive lobular carcinoma (CILC). METHODS: We retrospectively reviewed the medical records of 65 patients (4.0% of all invasive breast cancer patients) who underwent surgical excision for invasive lobular carcinoma (ILC) between January 2000 and November 2013. All 65 patients were diagnosed with ILC with negative immunohistochemical staining for E-cadherin in the tumor cells. All hematoxylin and eosin slides of the previously diagnosed ILC were reviewed and confirmed by two expert pathologists and we compared the clinicopathologic features between CILC and PILC. RESULTS: CILC was found in 46 cases and PILC, in 19 cases. Of the mammographic findings, a mass or asymmetric density was the most common feature (42.3% of all ILC patients). The most common ultrasonographic feature was a mass (94.9% of all ILC patients). Tumor multiplicity was noted in 10 patients (15.4%) among all ILC patients; eight patients (17.4%) had CILC and two patients (10.5%) had PILC. PILC patients had more grade III tumors (66.7% vs. 8.7%, p=0.002) and a higher Ki-67 labeling index (55.6% vs. 18.6%, p=0.004) than those with CILC. There were no statistical differences in the type of combined in situ component, extensive intraductal component, tumor size, lymphovascular invasion, stage, hormone receptor status, human epidermal growth factor receptor 2 status, distribution of intrinsic subtype, or imaging findings. Moreover, there was no significant difference in survival between CILC and PILC. CONCLUSION: PILC showed more pathological aggressiveness than CILC in terms of tumor grade and Ki-67 index.