Expression of the Thyroid Transcription Factor-1 in Carcinomas of Salivary Gland Type and Pulmonary Adenocarcinomas

ABSTRACT

BACKGROUND: Carcinomas of salivary gland type (CSGT) in the low respiratory tract are rare and often difficult to differentiate from pulmonary adenocarcinomas, which are more common and more aggressive than CSGT, especially in the biopsy specimens. Thyroid transcription factor-1 (TTF-1) is a tissue-specific transcription factor expressed in the thyroid gland and the lung. The purpose of this study is to elucidate the diagnostic utility of TTF-1 in discerning CSGT from adenocarcinomas in the low respiratory tract. METHODS: Immunohistochemical expression of TTF-1 was investigated in 14 CSGT (9 mucoepidermoid carcinomas and 5 adenoid cystic carcinomas) and 19 adenocarcinomas (5 well differentiated, 12 moderately differentiated and 2 poorly differentiated). RESULTS: Normal alveolar cells as well as bronchial epithelial cells showed the immunoreactivity for TTF-1, but not in the bronchial glands. In tumors, immunoreactivity for TTF-1 was identified in 17 out of 19 cases of adenocarcinomas (89%), but in none of 14 cases of CSGT. In adenocarcinomas, the immunoreactivity for TTF-1 was strongly correlated with the degree of differentiation (p<0.001). CONCLUSIONS: These results suggest that TTF-1 can be a valuable marker in distinguishing CSGT from adenocarcinomas of the low respiratory tract.