Axillary lymph node and non-sentinel lymph node metastasis among the ACOSOG Z0011 eligible breast cancer patients with invasive ductal, invasive lobular, or other histological special types: a multi-institutional retrospective analysis.

PURPOSE: Given the histological special types (HST) of breast carcinoma accounted for minority of the Z0011 study population, this study aimed to assess the rates of axillary lymph node (ALN) involvement and non-sentinel lymph node (SLN) metastasis in patients with invasive ductal carcinoma (IDC), invasive lobular carcinoma (ILC), or other HST. METHODS: Patients with cT1-2N0M0 breast cancer treated between 2009 and 2018 were retrospectively included from a multi-institutional database. Rates of nodal involvement were analyzed among different histological subgroups. The impact of ALN dissection (ALND) on adjuvant treatment decisions and prognosis were also analyzed among patients with 1-2 + SLNs. RESULTS: A total of 8294 patients were included: 6854 (82.6%), 257 (3.1%), and 1183 (14.3%) patients with IDC, ILC, and other HST, respectively. IDC patients had a significantly higher rate of ALN metastasis compared with ILC or other HST (31.9% vs. 22.6% vs. 16.4%, P < 0.001). However, in patients with 1-2 + SLNs, rates of non-SLN metastasis were similar among three groups (IDC: n = 182, 28.6% vs. ILC: n = 5, 31.2% vs. other HST: n = 29, 34.9%, P = 0.481). For patients with 1-2 + SLNs, rates of adjuvant chemotherapy and the estimated 3-year recurrence-free survival were similar between the SLN biopsy and ALND arms, regardless of the histological types. CONCLUSION: Among patients with 1-2 + SLNs, ILC or other HST had similar rates of non-SLN metastasis compared with IDC. Omission of ALND may not influence adjuvant chemotherapy usage or disease outcome regardless of histological types.