Significance of lung biopsy for the definitive diagnosis of lung nodules in breast cancer patients

The aim of the present study was to evaluate the significance of lung biopsy for the modification of the treatment strategy in breast cancer patients who develop lung nodules during follow-up after breast surgery. Of 53 consecutive patients who underwent lung biopsies in two institutions (Hiroshima University Hospital and Hiroshima Prefectural Hospital, Hiroshima, Japan) between 1997 and 2014, 45 underwent lung surgery and 8 underwent percutaneous or transbronchial tumor biopsy for lung nodules developing after curative surgery for breast cancer. The indications for lung biopsy included lung nodules for which a definitive diagnosis was difficult to achieve, and those for which the treatment strategy depended on the pathological diagnosis. The lung nodules were pathologically diagnosed as primary breast cancer metastases to the lungs in 25 (47%), primary malignant lung tumors in 21 (40%) and benign disease in 7 (13%) patients. Among the 25 metastatic patients confirmed by lung biopsy, phenotype discordance was observed in 6 patients (24%). A total of 3 patients with lung metastasis proven to have estrogen or progesterone receptor upregulation by lung biopsy received endocrine therapy. Univariate analysis revealed that patients with metastatic breast cancer confirmed by lung biopsy were significantly younger and had more locally advanced primary cancers diagnosed via clinical and pathological assessment compared with patients with other diseases. Therefore, mastectomy and axillary lymph node dissection were performed more frequently in the metastasis group compared with the others group. Multivariate analysis revealed that mastectomy (P<0.001) and axillary dissection (P<0.001) were independent factors predicting that the lung nodules would be metastases from breast cancer. Lung biopsy in breast cancer patients who developed lung nodules during the follow-up period after breast cancer surgery was crucial for making a definitive diagnosis and modifying the treatment strategy, which may improve the prognosis of breast cancer patients.