title: Clinicopathological and genetic heterogeneity of the head and neck solitary fibrous tumours: a comparative histological, immunohistochemical and molecular study of 36 cases.
abstract: OBJECTIVE
  Solitary fibrous tumour (SFT) harbours recurrent inv12(q13q13)-derived NAB2-STAT6 fusions, resulting in STAT6 nuclear expression. SFTs affecting the head and neck are rare, for which we reported their clinicopathological, immunohistochemical, and genetic features.
  
  
  RESULTS
  With 19 cases assessable for NAB2-STAT6 fusions, 36 head and neck SFTs (18 males; 18 females) diagnosed between 13 and 79 years (median, 47 years) of age were analysed for clinicopathological features and STAT6 immunoexpression. These SFTs, ranging from 5 to 80 mm (median, 25 mm), affected the oral cavity/pharynx (12), orbit (11), sinonasal structures (seven), and somatic soft tissues or skull (six). Histologically, 20 SFTs were conventional, six were giant-cell angiofibroma-like, one was fat-forming, four were cellular/atypical, and five were malignant (two developing metastases). STAT6 distinctively decorated the tumoral nuclei in 35 (97.2%) SFTs, but not in 29 site-relevant histological mimics categorized into 12 entities. Sixteen (84.2%) SFTs showed NAB2-STAT6 fusions with highly heterogeneous exon compositions, including NAB2ex6-STAT6ex17 in four cases, NAB2ex4-STAT6ex2 in three cases, NAB2ex2-STAT6ex2, NAB2ex4-STAT6ex4, NAB2ex6-STAT6ex16 and NAB2ex6-STAT6ex18 in two cases each, and NAB2ex3-STAT6ex19 in one case.
  
  
  CONCLUSIONS
  Nuclear STAT6 immunoexpression is sensitive and specific for distinguishing SFT from mimics. However, considerable heterogeneity exists in the head and neck SFTs regarding the locations, histological patterns, and NAB2-STAT6 fusion variants.
authors.affiliation: Department of Pathology, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Yu-Chien
authors.initials: YC
authors.lastname: Kao
authors.affiliation: Department of Orthopaedic Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Po-Chun
authors.initials: PC
authors.lastname: Lin
authors.affiliation: Department of Anatomical Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Shao-Lun
authors.initials: SL
authors.lastname: Yen
authors.affiliation: Department of Anatomical Pathology, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.
authors.forename: Shih-Chiang
authors.initials: SC
authors.lastname: Huang
authors.affiliation: Department of Anatomic Pathology, E-Da Hospital, Kaohsiung, Kaohsiung, Taiwan.
authors.forename: Jen-Wei
authors.initials: JW
authors.lastname: Tsai
authors.affiliation: Department of Pathology, Chi-Mei Medical Centre, Tainan, Taiwan.
authors.forename: Chien-Feng
authors.initials: CF
authors.lastname: Li
authors.affiliation: Department of Pathology, Changhua Christian Hospital, Changhua, Taiwan.
authors.forename: Hui-Chun
authors.initials: HC
authors.lastname: Tai
authors.affiliation: Department of Anatomical Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Jui
authors.initials: J
authors.lastname: Lan
authors.affiliation: Department of Anatomical Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: I-Chieh
authors.initials: IC
authors.lastname: Chuang
authors.affiliation: Department of Anatomical Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Shih-Chen
authors.initials: SC
authors.lastname: Yu
authors.affiliation: Department of Anatomical Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Hsuan-Ying
authors.initials: HY
authors.lastname: Huang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D002467:Cell Nucleus / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D006258:Head and Neck Neoplasms / Q000235:genetics* / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D015514:Oncogene Proteins, Fusion / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050800:STAT6 Transcription Factor / Q000096:biosynthesis / Q000235:genetics*; D054364:Solitary Fibrous Tumors / Q000235:genetics* / Q000473:pathology*; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; C491000:NAB2 protein, human; D015514:Oncogene Proteins, Fusion; D012097:Repressor Proteins; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human
keywords: NAB2; RT-PCR; STAT6; head and neck; solitary fibrous tumour