As only 4 of 21 patients in our review were diagnosed with CNS metastasis as a site of initial distant metastasis, and only 1 of those patients had MiM at the time of diagnosis of initial distant metastasis, it can be inferred that MiM may be a manifestation of progressive disease, and it appears to be a late site of metastasis in breast cancer (Table 3). This evidence concerns the gene MTSS1 and breast cancer.