BRAF and neoplasm: Interestingly, neither did the expression of BRAF V600E alone in the targeted stem/progenitor subpopulation result in the formation of intrinsic neoplasms, nor did the isolated loss of Ink4a/Arf; instead, the combined expression of BRAF V600E and loss of Ink4a/Arf, led to the development of poorly differentiated intrinsic neoplasms (incidence approximately 40%), with no glial marker expression.