Objective To investigate the micrometastatic lesion of tumor stem cells in the axillary swollen lymph nodes of breast cancer patients and the influence of miR30a on its invasive ability ,and to explore the feasibility of miRNAs anti‐breast cancer treatment .Methods The tumor stem cell‐like breast cancer cells were separated from the axillary swollen lymph nodes in breast cancer patients and cultured .miR30a oligonucleotide fragment was synthesized and transfected into human primary generation breast cancer cells by using adenovirus ,meanwhile the breast cancer cell line MDA‐MB‐231 was taken as the experimental control and the transfection efficiency was assessed by the fluorescence microscopy .The changes of tumor cell proliferation and invasiveness before and after transfection were detected by the Transwell chamber in vitro invasion assay .Western blot was used to detect the ALDH1 ,Vimentin and N‐Cadherin protein expression .Results The Transwell chamber in vitro invasion assay showed that the pri‐mary generation breast cancer cell had more strong invasive ability than MDA‐MB‐231 cell line ,their invasion indexes were (75 .3 ± 3 .2)% and (58 .4 ± 2 .8)% respectively ,the difference was statistically significant (P<0 .05) ,and after transfecting miR30a ,the in vitro invasiveness ability in these two kinds of cells were significantly weakened and their invasion indexes were (21 .4 ± 1 .9)% and (28 .2 ± 2 .3)% respectively ,the difference compared with the control group showed the statistical significance (P<0 .05) .Conclu‐sion The ALDH expression in partial axillary hyperplasia and swollen lymph nodes in the patients with breast cancer is increased , and the tumor micrometastasis may exist ,which should be completely cleaned in operation .miR30a inhibits the expression and inva‐sive ability of tumor stem gene .