Although identical TSC1 or TSC2 mutations among tumor cells are not always observed in TSC-LAM and S-LAM patients, it is clear that LAM cells are mobile; markedly, LAM cells are able to infiltrate and repopulate healthy donor lungs following transplantation (Bittmann et al., 2003; Karbowniczek et al., 2003). The gene discussed is TSC2; the disease is lymphangioleiomyomatosis.