In TN4, early truncal homozygous mutations (GRIN3A, PTPN4, AKAP6) along with copy-number losses (TP53, NOTCH3) and gains (DMKN, GRIN3A) co-occurred with TP53 in the MRCA at the earliest stages of tumor progression. The gene discussed is GRIN3A; the disease is neoplasm.