Is invasive lobular carcinoma different from invasive ductal carcinoma?

The purpose of this study is to determine whether the histopathologic features and outcome in invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC) are different, and whether the histologic type is a prognostic factor for outcome.

A retrospective cohort study was conducted in consecutive 510 stage I/II breast carcinoma patients who underwent modified radical mastectomy. The features of 65 patients with ILC were compared with those of 445 patients with IDC. In patients with median follow-up period of 44 months, univariate and multivariate prognostic factor analyses for cancer-specific death and relapse were carried out.

The median ages in patients with ILC and those with IDC were 52 and 41 (P=0.04). Tumor size, estrogen receptor positive expression and nodal positivity were not significantly different between the histologic types. Patients with ILC had more frequently (81.5%) low grade tumors and less lymphatic vascular invasion (9.3%) in primary tumor than those with IDC (P<0.05). Whereas the rates of 5-year overall survival were 94% in ILC and 90% in IDC, the rates of 5-year event-free survival were 71 and 67%, respectively (P=NS). Multivariate analyses in all patients demonstrated that tumor size, pathologic lymph node status and age at diagnosis were the most important prognostic factors for overall and event-free survival. Histologic type was not statistically significant for both outcomes.

Although patients with ILC had older age, low grade tumor and less lymphatic vascular invasion, they had no survival advantage comparing with their counterparts. Histologic type was not an independent prognostic factor for outcome.