ERBB2 and breast cancer: While MMTV-Neu/pBABE cells to wild-type FVB mice resulted in metastatic lung lesions in 41.7% of recipients, consistent with previous reports that MMTV-Neu mammary tumors metastasize to the lungs with a penetrance of approximately 30%, we found that 100% of MMTV-Neu/pBABE-Rictor recipients harbored lung metastases (Fig. 1g, left panel), and on average, harbored nearly twice as many metastatic lesion over recipients of MMTV-Neu/pBABE cells (Fig. 1g, right panel).