Metastatic pattern of invasive lobular carcinoma.

e11561 Background: Invasive lobular carcinoma (ILC) histology comprises around 10 percent of invasive breast cancers. To our knowledge, patterns of metastases over the entire disease course of ILC have been poorly described. Methods: Using a prospective registry in a single-institution academic oncology practice, we identified metastatic sites among women diagnosed with metastatic ILC or IDC between 1998 and 2012. Results: Among 694 patients, 615 (88.6%) had IDC and 79 (11.4%) had ILC histology. Pts with ILC had a higher median age at diagnosis of primary cancer and metastatic disease (p<0.01), a greater stage (III and IV) at the time of first cancer diagnosis (p=0.003), more hormone receptor-positive disease, fewer HER2-positive and triple negative tumors (p=0.003) compared with IDC. Median number of metastatic organ involvement was similar between IDC and ILC. Over the course of metastatic disease, more pts with IDC had visceral disease, lung, liver and ovarian metastases, but there was no difference be...