Abstract: Objective To study the diagnosis and treatment of occult breast cancer（OBC） with axillary lymph node metastasis as its primary clinical feature.Methods Clinical data about 12 OBC patients with axillary nodal metastasis as its primary clinical feature admitted to our hospital in January 2000-February 2009 were retrospectively analyzed.Of these patients,9 underwent breast magnetic resonance imaging of breast and axillary fossa.All patients underwent thyroid,thoracic and abdominal CT or PET-CT scanning before operation to exclude metastasis in other organs.Of the 12 patients,9 underwent axillary lymph node dissection and 3 underwent modified radical mastectomy.The biopsy samples were examined with immunohistochemistry.Of the 12 patients,3 underwent radiotherapy and 5 underwent endocrine therapy after operation.The longest and shortest follow-up time of the patients was 10 years and 1 year,respectively.Results OBC accounted for 0.77% in 1 550 breast cancer patients admitted to our hospital in January 2000-February 2009.Of the 12 OBC patients,2 was diagnosed with infiltrating ductal carcinoma,1 was diagnosed with infiltrating micropapillary carcinoma,with no foci observed in breast of the remaining 9 patients.The patients were followed up after operation,during which local recurrence was found in 1 patient and no distant metastasis occurred.Conclusion MRI is of great importance in diagnosis of OBC.Chemotherapy and neoadjuvant chemotherapy in combination with axillary lymph node dissection or modified radical mastectomy are the choice of treatment modalities for OBC.