Résumé
Intra-mammary lymph nodes (intra-MLN) are rare but associated with more aggressive breast cancer and seem to be a poor prognostic factor. The AJCC now recommends considering them as Berg stage 1 axillary node. Only few studies based on a small number of patients evaluated the prognosis of patients with positive intra-MLN, and none exists on how to treat an isolated positive intra-MLN.Methods: we conducted a retrospective, multicentric, matched case control study in 8 tertiary centers in France. 360 patients were included: 90 with a positive intra-mammary and negative axillary lymph node, and 270 with no lymph node metastasis. Both groups were matched on the age at diagnosis, the tumor size, the hormone receptor status and the HER2 status.Results: a positive intra-MLN is associated with reduced loco-regional recurrence-free survival (LRFS) (HR=3.38; p=0.0197), metastatic free survival (MFS) (HR=7.44; p<0.0001) and overall survival (OS) (HR=2.6; p=0.0185) in univariate analysis, despite more aggressive treatment. In multivariate analysis, it is an independent predictor of reduced MFS (HR= 5.71; p=0.002), but not of shorter LRFS and OS. Performing mastectomy, axillary dissection, chemotherapy and radiotherapy on chest wall and lymph nodes areas is not associated with better disease free survival.Conclusion: positive intra-MLN are a marker of disease severity and an independent predictor of poor outcome in breast cancer. More effort should be done to diagnose them on preoperative imaging, and furthers studies are needed to statute on the therapeutic management of patients with an isolated positive intra-MLN.