Loss of heterozygosity at the TSC1 or TSC2 locus and hyperphosphorylation of ribosomal protein S6 has been documented in each of the three cellular components of angiomyolipomas [6], suggesting that they may arise from a common progenitor and that the TSC1–TSC2 complex regulates the differentiation of cells that are derived from the mesenchyme. Here, TSC1 is linked to angiomyolipoma.