Characterization of novel USP6 gene rearrangements in a subset of so-called cellular fibroma of tendon sheath

Clinicopathological and molecular characterisation of USP6‐rearranged soft tissue neoplasms: the evidence of genetic relatedness indicates an expanding family with variable bone‐forming capacity

“…Herein, we confirmed the presence of MYH9 – USP6 in another intravascular NF, reinforcing its genetic commonality with ordinary NF. Following the identification of USP6 rearrangement in cellular FTS, various USP6 fusion partners were recently discovered, including PKM , RCC1 , ASPN , COL3A1 , COL1A1 , and MYH9 , with MYH9 being recurrent in two cases 20,21 . In seven USP6 ‐rearranged cellular FTSs, we also validated COL1A1 and MYH9 as the recurrent 5’ partner gene in two and four cases, respectively, highlighting the histological and genetic similarities between cellular FTSs and NFs.…”

“…Following the identification of USP6 rearrangement in cellular FTS, various USP6 fusion partners were recently discovered, including PKM, RCC1, ASPN, COL3A1, COL1A1, and MYH9, with MYH9 being recurrent in two cases. 20,21 In seven USP6-rearranged cellular FTSs, we also validated COL1A1 and MYH9 as the recurrent 5' partner gene in two and four cases, respectively, highlighting the histological and genetic similarities between cellular FTSs and NFs. Recently, the genetic similarity of cranial fasciitis to NF has also been demonstrated by Paulson et al, who performed targeted RNA sequencing on 15 cases, five of which were found to harbour rearranged USP6 juxtaposed to various 5 0 partners, including SERPINH1, COL3A1, SPARC, and MYH9.…”

“…2,[11][12][13][14][15][16][17][18][19] Among these, some potential NF variants were previously classified as other tumour entities; for instance, the cellular type of fibroma of tendon sheath (FTS) is now better regarded as tenosynovial NF after the recent identification of rearranged USP6. 20,21 However, other rare NF-associated settings still remain insufficiently characterised for USP6 and partner genes, including those affecting infants outside the cranial vault, originating from the vessels or body cavities, or undergoing various types of osseous metaplasia [also known as fasciitis ossificans (FO)]. 12,14,15,17,18 According to the current World Health Organization classification, myositis ossificans (MO) and fibroosseous pseudotumour of digits (FOPD) are grouped together as rapidly growing, self-limiting ST lesions with definite bone-forming capacity, 22 although they differ in their preferential sites and matrix-deposition patterns.…”

“…Most NF arise from the subcutaneous tissues as a circumscribed or infiltrative nodular lesion, whereas considerable clinicopathological diversity appears in minor subsets, regarding the rarities of tumoral sites and depth, presenting age, and variant histology 2,11–19 . Among these, some potential NF variants were previously classified as other tumour entities; for instance, the cellular type of fibroma of tendon sheath (FTS) is now better regarded as tenosynovial NF after the recent identification of rearranged USP6 20,21 . However, other rare NF‐associated settings still remain insufficiently characterised for USP6 and partner genes, including those affecting infants outside the cranial vault, originating from the vessels or body cavities, or undergoing various types of osseous metaplasia [also known as fasciitis ossificans (FO)] 12,14,15,17,18 …”

An Update on Clinicopathological, Imaging and Genetic Features of Desmoplastic Fibroblastoma (Collagenous Fibroma)

“…On the other hand, Carter et al recently reported that ubiquitin-specific protease 6 (USP6) (located on 17p13) rearrangements were found in approximately 67% of cellular fibroma of tendon sheath but not in classic fibroma of tendon sheath (26). Most recently, anchored multiplex polymerase chain reaction/nextgeneration sequencing revealed pyruvate kinase M1/2, regulator of chromosome condensation 1, asporin, collagen type I alpha 1 chain, collagen type III alpha 1 chain and non-muscle myosin heavy chain 9 as fusion partners for USP6 in cellular fibroma of tendon sheath (27).…”