Background: Infiltrating lobular carcinomas (ILC) represent approximately 10% of all breast cancers. The literature is mixed regarding their prognosis when compared with infiltrating duct carcinomas (IDC). There are few data regarding the treatment of ILC with radiation therapy.
Methods: The clinical, pathologic, laboratory, and survival data of 161 patients with ILC were compared with the data of 1138 patients with IDC.
Results: ILCs were larger, more difficult to excise completely, and more difficult to diagnose clinically. All prognostic factors measured were more favorable for ILC. Nodal positivity for ILC was 32%, compared with 37% for IDC (P = 0.22). The 7-year disease-free Kaplan-Meier survival (DFS) was 74% for patients with ILC and 63% for patients with IDC (P < 0.03). The 7-year breast cancer specific survival (BCSS) was 83% for patients with ILC and 77% for patients with IDC (P < 0.04). Selected patients with smaller lesions were treated with excision and radiation therapy. Patients with ILC treated with radiation therapy had a better DFS and BCSS than did patients with IDC treated with radiation therapy.
Conclusions: ILCs often are homogeneous, small cell tumors of low nuclear grade. Their desmoplastic reaction may be absent or less marked than that of IDC, making them more difficult to palpate and to visualize mammographically. Despite this, they can be treated successfully with either mastectomy or excision and radiation therapy.