CDKN2A and neoplasm: In addition to the ATRX mutations, 8 out of 9 ATRX-immunonegative tumors had other genetic abnormalities: inactivating somatic mutations in tumor suppressor genes TP53 (6), PTEN (2), RB1 (1), NF2 (1), and a homozygous deletion of CDKN2A/B in both primary tumor and metastasis in 1 patient (Table 3).