title: TTF-1 may not be a reliable marker for differentiating metastasis from brain tumors.
abstract: OBJECTIVE
  TTF-1 is widely used as an immunohistochemical marker of lung and thyroid tumors. However, TTF-1 expression has been described in tumors from other sites. The presence of TTF-1 expression in primary brain tumors is largely unclear and has not been clearly specified yet. We characterized expression of two TTF-1 clones in primary brain tumors with relevance to tumor types and grades.
  
  
  METHODS
  We studied immunohistochemistry with tissue micro-array, using both clones (8G7G3/1 and SPT24) in 45 primary brain tumors of different types and grades. Our cases consisted of 1 grade I, 7 grade II, 4 grade III, 20 grade IV astrocytic tumors; 9 meningiomas, 2 oligodendrogliomas, 1 schwannoma and 1 medulloblastoma.
  
  
  RESULTS
  We have found TTF-1 nuclear staining using the SPT24 clone in 4 cases (3 cases were grade IV and 1 was grade III). Focal and weak staining was seen in three cases and moderate-strong and diffuse staining was seen in one case. All the tumors were negative with clone 8G7G3/1. Clone SPT24 was more sensitive but less specific.
  
  
  CONCLUSIONS
  TTF-1 can also be expressed in primary brain tumors, particularly grade III to IV tumors. TTF-1 expression was a rare finding in previous studies, however strong and diffuse staining was not observed until today. We think that TTF-1 nuclear expression in high-grade astrocytic tumors cannot rule out primaries even when diffuse and strong staining. Clinical and pathological parameters should be evaluated together.
authors.affiliation: Department of Pathology, Akdeniz University, Faculty of Medicine, ANTALYA, TURKEY.
authors.forename: Betül
authors.initials: B
authors.lastname: Unal
authors.forename: Senay
authors.initials: S
authors.lastname: Yildirim
authors.forename: Cem
authors.initials: C
authors.lastname: Sezer
authors.forename: Dinç
authors.initials: D
authors.lastname: Süren
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D001932:Brain Neoplasms / Q000175:diagnosis*; D004268:DNA-Binding Proteins / Q000032:analysis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000175:diagnosis*; D046888:Tissue Array Analysis; D014157:Transcription Factors
chemical_list: D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; C504003:TTF1 protein, human; D014157:Transcription Factors