title: TTF-1 expression is specific for lung primary in typical and atypical carcinoids: TTF-1-positive carcinoids are predominantly in peripheral location.
abstract: Thyroid transcription factor (TTF)-1 expression in neuroendocrine tumors (NETs) has not been studied as widely as that in non-NETs, with the exception of small cell carcinomas, in which TTF-1 is highly sensitive but not specific for a primary lung tumor. The reported incidence of TTF-1 expression in pulmonary carcinoids has also been highly variable in the literature. To evaluate the expression of TTF-1 in NETs and potential value of TTF-1 in distinguishing pulmonary NETs from those of extrapulmonary origin, we performed an immunohistochemical study by using semiquantitative analysis on formalin-fixed, paraffin-embedded sections from 111 NETs, including 80 pulmonary (11 carcinoid tumorlets [TLs] or foci of neuroendocrine cell hyperplasia [NEH], 36 typical carcinoids [TCs], 17 atypical carcinoids [ACs], 16 large cell neuroendocrine carcinomas [LCNECs]), 13 thymic (3 TCs, 8 ACs, 2 LCNECs), 17 gastrointestinal or pancreatic (13 TCs, 4 ACs), and 1 ovarian (LCNEC). Pulmonary carcinoids were subdivided into those with central and those with peripheral location. TTF-1 positivity was seen exclusively in pulmonary NETs and was significantly higher in NEH or TLs (72.7%) than in TCs (27.8%), ACs (29.4%), and LCNECs (37.5%; P = 0.03). All extrapulmonary NETs were uniformly negative for TTF-1 staining. Interestingly, 12 of 14 TTF-1-positive pulmonary TCs and ACs had a peripheral location with spindle cell morphology, as did all cases of TL, a purported precursor of peripheral carcinoids. In conclusion, TTF-1 expression was 100% specific, though not so sensitive, for the lung primary in TCs and ACs and possibly also in LCNECs. Prevalent TTF-1 positivity in TLs and peripheral carcinoids suggest that they may be histogenetically distinct from the central carcinoids, which are typically composed of TTF-1-negative, more rounded cells.
authors.affiliation: Department of Pathology, University of California San Diego Medical Center, San Diego, CA 92103-8720, USA.
authors.forename: Emma Z
authors.initials: EZ
authors.lastname: Du
authors.forename: P
authors.initials: P
authors.lastname: Goldstraw
authors.forename: Jo
authors.initials: J
authors.lastname: Zacharias
authors.forename: Olivier
authors.initials: O
authors.lastname: Tiffet
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Craig
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Nicholson
authors.forename: Noel
authors.initials: N
authors.lastname: Weidner
authors.forename: Eunhee S
authors.initials: ES
authors.lastname: Yi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D002276:Carcinoid Tumor / Q000378:metabolism* / Q000473:pathology; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000378:metabolism*; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; C000614412:NKX2-1 protein, human; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors