Taya et al. [40] detected that the ECD of GPNMB fell off from the cell surface of TSC2-deficient cells and entered the circulation, and the soluble GPNMB content in serum of LAM patients was significantly higher than that of healthy control samples, suggesting that GPNMB could be used as a new biomarker for the diagnosis of LAM. This evidence concerns the gene TSC2 and lymphangioleiomyomatosis.