FLG2 and neoplasm: To explain the existence of non-mutated IFPs exist, they proposed two hypotheses: (i) the low ratio of tumor cells in small lesions leads to false-negative results in mutational analysis; and (ii) mutational analysis can be negative because small lesions do not have oncogenic mutations and remain ‘pre-IFP’, but once the PDGFRA mutation occurs, the lesions start growing and evolving towards IFPs [19].