Regional lymph node status is the most important prognostic factor for disease-free and overall survival in breast cancer. Accurate nodal staging can be achieved only by surgery. Today, in early-stage invasive breast cancers with clinically negative lymph nodes, minimally invasive sentinel lymph node biopsy (SLNB) is considered the gold standard of regional lymph node staging. To optimize the effectiveness of SLNB, precise pre-and intraoperative mapping of lymphatic drainage is important. The (SLNB) technique is not standardized. The most common and most accurate way of lymphatic mapping is performed with the combined application of a gamma-emitting isotope labeled substance and blue dye, the so-called double labeling technique. Functional lymphatic drainage of SLNB double staining in the mammary gland, skin and axilla present a number of uncertainties.

According to the axillary, lateral thoracic and thoracodorsal veins, Ibusuki et al. divided the axillary region into four subregions: brachial (lateral), pectoral (anterior), central and subscapular (posterior) zones. They revealed clear relationship between the anatomic location and status of the SLN, also confirmed by Gallowitsch et al. SLN was detected in Level I in 96% and in Level II in 4% by SPECT/CT.

Knowedge of relationships between the drainage of sentinel lymph node staining into the axillary subregions, location of the primary tumor, tumor size, SLN positivity and its location within the subregion are of particular importance in the decision making whether or not axillary lymphadenectomy (ALND) needs to be performed.

In the prospective randomized phase 3 trial by Giuliano et al. (ACOSOG Z-11) ALND was not performed in early breast cancer patients with clinically negative axilla and breast-conserving surgery, for 1-2 macroscopically positive SLNs (10). After an average follow-up of 6.3 years, data were compared to the traditional ALND group and no difference was detected in 5-year overall survival or disease-free survival at 5 years.

Aims of the investigation:

To examine the location of SLN in the axillary subregion (anterior, posterior, central, lateral, apical) in patients with early breast cancer (T <5 cm).

To statistically assess correlations between the location, size, histological parameters of primary breast tumor and the subregion of the SLN.

To statistically assess SLN positivity and its location within the sbregion.

To statistically assess subregional localisation of positive SLN and the number of all positive regional lymph nodes, to predict a limited number of cases with lymph node metastasis, based on the test results of the ACOSOG Z-11 trial, by which ALND could be omitted.

Inclusion Criteria:

• women with clinically node negative invasive or microinvasive breast cancer: T1-2(≤ 5cm)N0M0
• 18 years of age or older

Exclusion Criteria:

• previous ALND
• clinically positive axillary SLNB
• pregnant or lactating
• neoadjuvant breast cancer treatment based on surgeon's discretion (ASCO)

Clinical stage T1-2(≤ 5cm)N0M0 primary unilateral invasive breast cancer patients