This is a multicentre, non-interventional, prospective study to be carried out in representative oncology departments / institutions in order to determine the association between the presence of germline DNA-repair genes mutations and PD-L1 expression level in tumour and immune cells in breast cancer. No additional procedures besides those already used in the routine clinical practice will be applied to the patients.

Breast cancer (BC) occupies the first place among malignancy in females (29.9% of all tumors in female patients in Russian Federation in 2015) [1].

One of the most perspective direction of the oncotherapy is anticancer immunotherapy - employment of inhibitors of immune checkpoints. Immune checkpoints inhibitors (such as anti-PD-1 and anti-PD-L1 antibodies) have shown good clinical efficiency in clinical research to cure such malignant tumor with high mutation load, as melanoma, lung cancer, and others.

One of the hypothesis of such effect states that, usually, more cancer neoantigens are synthetized in the tumors with high mutation load (driven by genome instability), causing severe lymphoid infiltration [2-3]. This situation is balanced by overexpression of such inhibitors of the immune response as PD-1 and PD-L1 [4 - 6].

Breast cancer - is relatively heterogenic tumor, with different genetic, morphological and phenotypic forms.

Despite relatively low expression of PD-L1 in BC in general, there are reasons to believe that genetic instability, driven by mutations in genes involved in DNA repair, can increase the immunogenicity and, thus, the expression of PD-L1 in BC.

To date, it is widely accepted that 5-10% of BC cases are represented by hereditary types, i.e. mediated by germline pathogenic mutations in genes of DNA reparation pathways. Hereditary breast cancer (HBC), as well as ovarian cancer (OC), сaused by mutations in genes BRCA1, BRCA2, CHEK2, TP53 и PTEN, and others. Thus, one of the promising directions here is to understand the inter-relation among germline pathogenic mutations associated with HBC, and activity of PD-L1. It would allow to optimize selection of anti-PD-L1 therapy, by forming group of patients (matching criteria of HBC) with high level of PD-L1 expression in cancer cells and tumor-infiltrating lymphocytes.

Inclusion Criteria:

• 1. The voluntary obtained informed consent signed by both the subject and the investigator.

  2. Females 18 years age or more. 3. Histologically confirmed BC with known hormone receptors and HER2neu receptors status, Grade of tumor, diagnosed before enrolment into the study.

  4. Availability of FFPE tissue samples received prior to any type of antitumor treatment start. Tumour tissue samples must be satisfied IHC requirements for PD-L1 testing.

  5. Ability of blood samples receiving for NGS germline mutations testing. 6. Completed medical records (stage, receptors status, demographic data)

Exclusion Criteria:

• Any evidence of uncontrolled system pathology, active infections, active bleeding diathesis, renal graft, including virus hepatitis B, C or HIV.

patients, female aged between 18-80yrs with breast cancer