Tumor characteristics predictive of sentinel node metastases in 105 consecutive patients with invasive lobular carcinoma

Background: Identification of nodal metastases in invasive lobular carcinoma (ILC) is difficult. Sentinel node (SN) biopsy offers a potential advantage. This study reports the feasibility of SN identification and predictors of SN metastases for ILC. Methods: All cases of ILC undergoing sentinel lymphadenectomy between October 1991 and May 2001 were evaluated. Patients enrolled in ACOSOG Z0010/Z0011 were excluded. Presentation, surgical treatment, tumor characteristics, and prognostic factors were analyzed for statistical significance. Results: SN mapping was performed in 105 patients with 106 cases of ILC. SN identification was 97%, accuracy 100%, and positivity 50% with 45% macrometastases, 16% micrometastases, and 39% immunometastases. There are no axillary recurrences at 43.73 months. Palpable tumor, increasing tumor size, and angiolymphatic invasion are statistically significant for SN-positive status. Conclusions: SN staging for ILC is feasible and accurate. Receptor status and proliferative indices are not useful markers for metastases. However, large tumor size and presence of angiolymphatic invasion are positive predictors.