We took advantage of the relatively smaller size of Trp53-/-Notch1-/-Notch2-/-, Trp53-/-Notch1-/-, and Trp53-/-Notch2-/- tumors and hyperplasias compared to Trp53-/-Rbpj-/- tumors to better define the prevalent sites of tumor formation within the forebrain after genetic inhibition of Notch and p53 (Figure 5, Table S1). The gene discussed is NOTCH1; the disease is neoplasm.