Prospective multicenter comparison of proliferation and other prognostic factors in lymph node negative lobular invasive breast cancer

Evaluation of prognostic factors in lymph node negative (LNneg) invasive lobular cancers (ILCs). Prospective analysis of proliferation and other prognosticators in 121 LNneg ILCs (119 months median follow-up, range 19–181), without adjuvant chemotherapy. ILC subtype was assessed in accordance with WHO-2003 criteria. Immunohistochemical E-cadherin and estrogen receptor were used. With a median follow up time of 83 months (range 19–181), 30 of the 121 (25%) ILC patients developed distant metastases and 27 (22%) died. None of the cases classified as solid/pleomorphic lobular were E-cadherin or estrogen receptor positive, contrasting the other ILCs. The solid/alveolar ILCs (n = 17) had a worse survival (50%) than the other ILCs (n = 104; 83%, P < 0.0001). Mitotic activity index (MAI) (but not nuclear grade or tubule formation) was prognostic with a threshold 0–5 versus >5 (=MAI-5) (contrasting MAI < 10 vs. ≥10 in breast cancers in general; 85 and 54% survival, P < 0.0001). In multivariate analysis only subtype and MAI but none of the other characteristics had independent prognostic value. Histologic subtype and MAI have independent prognostic value in node negative invasive lobular cancers.