Invasive lobular breast cancer: subtypes and outcome.

Invasive lobular carcinoma (ILC) is the most common "special type" of breast cancer. Although conflicting literature data are available on the outcome of ILC, recently reported data indicate that ILC carries a poorer prognosis if compared to invasive ductal carcinomas. We evaluated clinical and biological features of 981 consecutive patients with pT1-3, pN1-3 M0 ILC. Median follow-up was 7.4 years for survival. A total of 541 patients were classified as classic (55.8%), 146 alveolar (14.9%), 145 mixed non-classic (14.8%), 104 solid (10.6%), and 38 trabecular (3.9%). A statistically significant difference in the outcome was observed at multivariate analysis for patients with solid (HR 2.44, 95% CI 1.39-4.29 for OS; HR 1.92, 95% CI 1.29-2.88 for DFS) and mixed non-classic (HR 1.99, 95% CI 1.12-3.53 for OS) versus patients with classical ILC. A statistically significant difference in the risk of distant metastases was observed at multivariate analysis for patients with Luminal B (HR 2.56, 95% CI 1.38-4.76), HER2 positive (HR 7.80, 95% CI 1.55-39.3), and triple negative (HR 7.61, 95% CI 2.63-22.1) subtypes versus patients with Luminal A ILC. Age ≥70 years, tumor size and degree of nodal involvement were additional independent predictors of reduced overall survival. The outcome of ILC significantly correlated with histological and immunohistochemically defined molecular subtypes. New tailored strategies should be explored in these subgroups of patients with poor outcome.