We stratified our patients into three risk groups: 1) High-risk: VSCC associated with LS and showing PTCH1 under-expression; 2) Moderate-risk: a tumour either arising from LS or showing PTCH1 under-expression; 3) Low-risk: tumour neither associated with LS nor showing PTCH1 under-expression. The gene discussed is PTCH1; the disease is Leigh syndrome.