In breast cancer patients, venous drainage of the breast may contain cells of immunological importance, tumor cells undergoing dissemination and other biological factors derived from the tumor microenvironment.Collecting axillary venous blood during modified radical mastectomy and thus before dilution in the circulation may allow us to define biological properties of the tumor microenvironment.The aims of the present are: 1) develop a surgical approach to collect blood from the breast tumor microenvironment through tributaries of the axillary vein; 2) characterize and compare cells having immunological significance collected from the axillary vein with those in peripheral blood of breast cancer patients.We enrolled 17 women aging 30-50 years and diagnosed with breast cancer by mammography,ultrasound and biopsy (stages Ⅱ-Ⅲ).All patients were, pre-operatively, treatment-naive.During routine surgical dissection, 10 ml of blood was collected from tributaries of the axillary vein and 10 ml from peripheral blood in heparin tubes.Mononuclear cells were separated and percentages of different leukocytes were determined by flow cytometry.