Data from cohorts, prospective studies and one randomized trial (ASCOG Z0011) support the hypothesis that omission of additional axillary dissection in case of positive sentinel node has a limited impact on overall survival and relapse free survival. However, these data are not sufficient enough to recommend, as a standard of care, to avoid axillary dissection in case of positive sentinel node. The ASCOG Z0011 trial has been closed before the end of inclusions and the predefined non inferiority margin was found to be too large (5% difference at 5 years for primary endpoint).

Prospective randomized trial is then urgently mandatory before omission of axillary node dissection becomes a usual practice without a sufficient scientific level of proof. Indeed, in several reviews, the rate of omission of axillary node dissection in case of micrometastasis increased (Bilimoria) despite any strong proof has been demonstrated.

The omission of axillary node dissection in case of positive sentinel node may have strong practical impacts on patients but also on medical and economical aspects: in avoiding a prolonged hospitalisation, secondary morbidities due to axillary dissection requiring secondary care and their costs, as well as costs for secondary axillary dissection (14 to 25% in case of positive sentinel node) and finally shortening surgery duration.

The main investigator propose a Non Inferiority Randomized Multicenter Phase III Trial of Axillary Node Dissection Versus no Axillary Node Dissection in Case of Positive Sentinel Lymph Node in Invasive Breast Cancer

Inclusion Criteria:

1. - Patient aged 18 years and above,
2. - Patient with invasive breast cancer histologically proven or cytologically proven by fine needle biopsy,
3. - Patient with a unifocal tumor T0 - T1 - T2 up to 5 cm (clinical or in imagery), without previous therapy (neoadjuvant chemotherapy or hormone therapy),
4. - Patient with clinical N0 status,
5. - Absence of clinically detectable metastases known,

6- Patients for whom conservative surgery with sentinel lymph node (SLN) technique is feasible from the start in terms of carcinologic,

7 -All patients with lymph node involvement (GS+), whatever the size of the metastasis (macro-metastasis, micro-metastasis, cellular cluster or isolated tumor cells),

8 - Patient affiliated to a social security system or benefiting from such a system,

9 - Signed consent to participate.

Exclusion Criteria:

1. - Tumor of more than 5 cm
2. - Indication of neoadjuvant therapy by chemotherapy or hormone therapy
3. - History of breast cancer (ipsilateral, ie recurrence, or contralateral breast)
4. - History of any other invasive cancer other than a past cutaneous cancer correctly treated
5. - Initial metastatic disease known
6. - Presence of clinical axillary adenopathy
7. - Contra-indication to surgical excision
8. - Contra-indication to the SLN technique
9. - Pregnant women, of child-bearing potential, or lactating women

10- Patient deprived of liberty or under supervision of a guardian

11- Impossibility to undergo medical examinations of the study for geographical, social or psychological reasons.