CDKN2A and medulloblastoma: Homozygous deletions of (i) the 9p21.1–p21.3 region encompassing CDKN2A, CDKN2B and ARF and (ii) the 6q23.1 region, each observed in a single cell line, have previously been reported in medulloblastoma and other cancer types [7], [8], [15], [16].