Invasive lobular breast carcinoma: pleomorphic versus classical subtype, associations and prognosis

Abstract Background Invasive pleomorphic lobular carcinoma (IPLC) has been associated with a worse prognosis compared with classic invasive lobular carcinoma (cILC); however, studies are small and conflicting. We seek to examine the prognosis of women with IPLC compared with cILC. Methods A retrospective review of women with breast cancer at a single institution from 2003 to 2012 identified 193 women with invasive lobular carcinoma (ILC). IPLC was defined as ILC with a pathological description of primarily pleomorphic features and Nottingham histological grade score of 7, 8, or 9 or overall grade of 3 or mixed classic/pleomorphic features and overall grade of 3. All others were designated cILCs. Clinicopathologic variables, progression-free survival (PFS), per STEEP criteria, and overall survival (OS), using all-cause mortality, were examined in both groups. Results Of the 193 women, 46 (24%) had IPLC and 147 (76%) had cILC. The IPLC group had significantly higher stage at diagnosis and more Hispanic women, but there were no differences in other clinicopathologic features or treatment. Median follow-up was 57 months (0.1-155 months). In univariate analysis, IPLC was associated with worse PFS (log-rank P  = .09, Wilcoxon P  = .01) but no significant differences in OS (log-rank P  = .20, Wilcoxon P  = .16). In multivariate models adjusting for stage, IPLC was not significantly associated with PFS (hazard ratio [HR] 1.43; 95% confidence interval [CI], 0.73-2.79; P  = .30) or OS (HR 1.52; 95% CI, 0.58-4.01; P  = .40). Conclusions IPLC was initially associated with worse PFS, but this was attenuated after adjustment for cancer stage, and there were no differences in OS.