title: Expression of thyroid transcription factor-1 is associated with a basal-like phenotype in breast carcinomas.
abstract: BACKGROUND
  The differential diagnosis between primary and secondary breast cancers might be difficult, especially in poorly differentiated tumors. Thyroid Transcription Factor-1 (TTF-1) has been regarded as a reliable marker for lung or thyroid origin, with only occasional positive staining in other tumors. However, positive cases have recently been reported among primary breast carcinomas.
  
  
  RESULTS
  Here, we analyzed expression of TTF-1 protein (clone SPT24) by immunohistochemical staining of sections from paraffin embedded tumor samples in 247 primary breast cancers from the population-based Norwegian Breast Cancer Screening Program. Positive staining (weak or strong) was observed in 7 cases (2,8%). As novel observations, positivity was demonstrated more frequently in estrogen receptor negative cases (14,0% vs. 1,4%; p = 0,004), highly proliferative tumors (8,8% vs. 1,1%; p = 0,008), tumors with a basal-like phenotype by showing expression of CK5/6 and/or P-cadherin (11,1% vs. 1,4%; p = 0,01), and tumors with blood vessel invasion (9,7% vs. 1,9%; p = 0,04). Also, TTF-1 was associated with histological grade 3 tumors compared with grade 1 or 2 tumors (7,7% vs. 1,5%; p = 0,04) as well as lymph node positive cases (5,2% vs. 1,8%; p = 0,03).
  
  
  CONCLUSIONS
  Our population-based findings indicate that TTF-1 may be positive in approximately 3% of primary breast cancers, and positivity indicates an association with adverse prognostic factors.
  The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8313753509421182.
authors.affiliation: Department of Pathology, Vestfold Hospital Trust, Tønsberg, Norway. tor.klingen@siv.no
authors.forename: Tor A
authors.initials: TA
authors.lastname: Klingen
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.forename: Pål
authors.initials: P
authors.lastname: Suhrke
authors.forename: Ingunn M
authors.initials: IM
authors.lastname: Stefansson
authors.forename: Marian D
authors.initials: MD
authors.lastname: Gundersen
authors.forename: Lars A
authors.initials: LA
authors.lastname: Akslen
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D001943:Breast Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics*; D010641:Phenotype; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics; D011960:Receptors, Estrogen / Q000378:metabolism; D013961:Thyroid Gland / Q000378:metabolism* / Q000473:pathology; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; D015820:Cadherins; D009687:Nuclear Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; C000614412:NKX2-1 protein, human