“…4 In one study, most cases of NF (over 90%) had USP6 gene fusions, and in over half of those cases the USP6 fusion partner was MYH9 . 5 Rare cases of NF (proven to harbor USP6 fusions) have been described in joints 4,6 ; therefore, it has been proposed that CFTS might represent a tenosynovial variant of NF. However, thus far, in contrast to classic cases of NF, it would seem that the majority (but not all) of CFTSs have non - MYH9 USP6 fusions, so while there is clearly significant histologic and molecular overlap between these lesions, CFTS are perhaps more diverse than NF on a molecular level given a broader spectrum of non- USP6 fusion partners.…”