A TTR of 37% (95% CI 23–55%) was obtained by exploring only CDKN2A alteration (INK4a) using the AdCre method [28] and a TTR of 82% (95% CI 60–95%) from exploring the PDGS;Cre method [29]; these were primarily in benign tumors with few tumors showing atypical features and with other pathologies such as osteomas (78% and 88%, respectively) and hydrocephalus (56% and 31%, respectively). Here, CDKN2A is linked to Hydrocephalus.