RATIONALE: Studying samples of blood and tissue from patients with basal cell nevus syndrome and from healthy participants in the laboratory may help doctors learn more about changes that may occur in DNA and identify biomarkers related to basal cell nevus syndrome. Chemoprevention is the use of certain drugs to keep cancer from forming, growing, or coming back. The use of sirolimus may keep basal cell skin cancer from forming in patients with basal cell nevus syndrome.