Starting from the observation that breast tumors which preferentially metastasize to lung are characterized by low TSC1/2 expression and possibly by activated mTORC1 signaling, this study reveals five novel biomarkers for LAM lesions: two recognized lung metastasis mediators, FSCN1 and ID1, and three recognized stem and/or progenitor cell regulators, ALDH1, CD61, and SOX9. The gene discussed is SOX9; the disease is lymphangioleiomyomatosis.