The occurrence of LOH of both the NF1 and INK4b/ARF/INK4a regions has been investigated in tumor specimens of a small subset of our NF1 patients, and was reported for the first time in DNF, PNF, and astrocytoma, indicating that the genes included in the deletion interval may have a role in the tumorigenesis progression. This evidence concerns the gene CDKN2A and neoplasm.