TTF-1 expression is specific for lung primary in typical and atypical carcinoids: TTF-1-positive carcinoids are predominantly in peripheral location

• Published in: Human pathology 2004-07, Vol.35 (7), p.825-831
• Main Authors: Du, Emma Z, Goldstraw, P, Zacharias, Jo, Tiffet, Olivier, Craig, Paul J, Nicholson, Andrew G, Weidner, Noel, Yi, Eunhee S
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Biological and medical sciences; Biomarkers, Tumor - metabolism; carcinoid; Carcinoid Tumor - metabolism; Carcinoid Tumor - pathology; Cell Nucleus - metabolism; Cell Nucleus - pathology; Classification; Cloning; Female; Gene expression; Humans; Immunohistochemistry; Investigative techniques, diagnostic techniques (general aspects); large cell neuroendocrine carcinoma; Lung Neoplasms - metabolism; Lung Neoplasms - pathology; Male; Medical sciences; Middle Aged; neuroendocrine hyperplasia; Nuclear Proteins - metabolism; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Proteins; Thyroid Nuclear Factor 1; Transcription Factors - metabolism; TTF-1; tumorlet; Tumors
• ISSN: 0046-8177; 1532-8392
• DOI: 10.1016/j.humpath.2004.02.016

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.