Occult Axillary Node Metastases in Breast Cancer Are Prognostically Significant: Results in 368 Node-Negative Patients With 20-Year Follow-Up

Purpose In breast cancer, sentinel lymph node (SLN) biopsy allows the routine performance of serial sections and/or immunohistochemical (IHC) staining to detect occult metastases missed by conventional techniques. However, there is no consensus regarding the optimal method for pathologic examination of SLN, or the prognostic significance of SLN micrometastases. Patients and Methods In 368 patients with axillary node-negative invasive breast cancer, treated between 1976 and 1978 by mastectomy, axillary dissection, and no systemic therapy, we reexamined the axillary tissue blocks following our current pathologic protocol for SLN. Occult lymph node metastases were categorized by pattern of staining (immunohistochemically positive or negative [IHC±], hematoxylin-eosin staining positive or negative [H & E ±]), number of positive nodes (0, 1, > 1), number of metastatic cells (0, 1 to 20, 21 to 100, > 100), and largest cluster size (≤ 0.2 mm [pN0i+], 0.3 to 2.0 mm [pN1mi], > 2.0 mm [pN1a]). We report 20-year res...