Tumor characteristics and patient outcomes are similar between invasive lobular and mixed invasive ductal/lobular breast cancers but differ from pure invasive ductal breast cancers

BackgroundThe aim of this study was to investigate the clinical characteristics associated with invasive lobular cancer (ILC) and mixed invasive ductal cancer (IDC) and ILC compared with IDC.MethodsFrom 1996 to 2006, 4,336 patients with IDC, ILC, and mixed breast cancers were identified. Clinical variables were compared using χ2 and Fisher's exact tests. Kaplan-Meier survival curves were constructed.ResultsPatients included 3,595 (83%) with IDC, 480 (11%) with ILC, and 261 (6%) with mixed cancers. Patients with ILC and mixed cancers were more likely to have low-grade and estrogen-positive and progesterone-positive tumors but were diagnosed at higher stages of disease compared with patients with IDC (P < .05 for each). Patients with IDC had the poorest 5-year (80%) and 10-year (61%) survival compared with patients with ILC (87% and 68%) and mixed (84% and 69%) cancers (P = .029).ConclusionsAlthough patients with ILC and “mixed” cancers are diagnosed with more advanced disease, their survival is superior to patients with IDC.