Is Lobular Histology a Predictor of Sentinel Node Positivity in Early Breast Cancer? An Integrated Analysis of Histological Subtype and Preoperative Imaging?

Purpose: To assess whether lobular histology independently predicts sentinel lymph node biopsy (SLNB) positivity in early-stage clinically node-negative (cN0) breast cancer (BC), to identify other predictive factors of SLNB positivity, and to evaluate the diagnostic performance of preoperative axillary imaging. The cumulative incidence of local and distant recurrences were also evaluated. Methods: We retrospectively analyzed 661 patients with early-stage, cN0 BC undergoing surgery with SLNB. Clinical, pathological, and radiological data were assessed. Univariate and multivariate analyses were performed to identify predictors of SLNB positivity. The cumulative incidence of axillary and distant recurrences were calculated including only patients with at least 2 years follow up, for a total of 495 patients. Results: ILC was present in 16.9% of cases. SLNB positivity occurred in 16.1% of invasive lobular cancers (ILC) and 20% of nonspecial type tumors (NST) (P = .3). No significant differences in axillary lymph node dissection (ALND) rates or nodal upstaging were found between histologies. Tumor size > 20 mm and vascular invasion were independent predictors of SLNB positivity. Axillary ultrasound and magnetic resonance (MRI) showed high specificity (95% and 79%) and negative predictive value (80% and 98%) in identifying node-negative patients. No axillary recurrences occurred after a median follow-up of 49.3 months. Conclusions: ILC does not independently predict SLNB positivity or nodal upstaging. Tumor size and vascular invasion remain the strongest predictors. Axillary ultrasound and MRI are reliable tools to guide de-escalation. SLNB omission in well-selected cN0 patients, including those with ILC, may be considered in tailored and selected patients.