In search for other potential contributors to the increased risk of malignancy in LAM, we investigated relevant demographic, geographic, educational and clinical characteristics such as lung function, CT grades, VEGF-D levels, renal AMLs, and retroperitoneal tumors etc., we did not find any risk factor associated with increased malignancy risk in LAM (data not shown). This evidence concerns the gene VEGFD and lymphangioleiomyomatosis.