Neoadjuvant chemotherapy (NC) is an established therapy in breast cancer, able to downstage positive axillary lymph nodes, but might hamper their detectibility. Even if clinical observations suggest lower lymph node yield (LNY) after NC, data are inconclusive and it is unclear whether NC dependent parameters influence detection rates by axillary lymph node dissection (ALND).

We analyzed retrospectively the LNY in 182 patients with ALND after NC and 351 patients with primary ALND. Impact of surgery or pathological examination and specific histomorphological alterations were evaluated. Outcome analyses regarding recurrence rates, disease free (DFS) and overall survival (OS) were performed.

Axillary LNY was significantly lower in the NC in comparison to the primary surgery group (median 13 vs. 16; p < 0.0001). The likelihood of incomplete axillary staging was four times higher in the NC group (14.8% vs. 3.4%, p < 0.0001). Multivariate analyses excluded any influence by surgeon or pathologist. However, the chemotherapy dependent histological feature lymphoid depletion was an independent predictive factor for a lower LNY. Outcome analyses revealed no significant impact of the LNY on local and regional recurrence rates as well as DFS and OS, respectively.

NC significantly reduces the LNY by ALND and has profound effects on the histomorphological appearance of lymph nodes. The current recommendations for a minimum removal of 10 lymph nodes by ALND are clearly compromised by the clinically already established concept of NC. The LNY of less than 10 by ALND after NC might not be indicative for an insufficient axillary staging.