TSC1 and lymphangioleiomyomatosis: Based on the results from ours and others, we think the reasons leading to lack of detectable TSC1/2 mutations in some LAM patients could be categorized into two groups: technical reasons in which the methods used failed to identify the TSC1/2 mutations present in LAM patients and biological reasons in which mutations in some non-TSC1/2 genes, independently or synergizing with TSC1/2, might have contributed to tumorigenesis of S-LAM.