Prognostic significance of thyroid transcription factor-1 expression in both early-stage conventional adenocarcinoma and bronchioloalveolar carcinoma of the lung.

Thyroid transcription factor 1 (TTF-1) is a diagnostic immunohistochemical marker for primary pulmonary neoplasms, but its utility as a prognostic marker is not well established. Surgical specimens from 100 cases of pulmonary adenocarcinoma were retrieved from the hospital computer system, including 50 cases of conventional adenocarcinoma (CA) and 50 cases of bronchioloalveolar adenocarcinoma (BAC) (32 nonmucinous type and 18 mucinous type). Representative sections were immunostained for TTF-1. Positive immunohistochemical study was correlated with other prognostic parameters. In the CA group, strong or moderate TTF-1 expression was seen in 30 of 50 (60%) patients and was associated with significantly better survival compared with those patients having weak staining (7 cases; 14%) or negative staining (13 cases; 26%) (P <0.01; log-rank test). Spearman and Pearson's correlation showed no significant correlation between TTF-1 expression and tumor grade, size, recurrence, or vascular invasion; therefore, TTF-1 was considered an independent predictor of survival. In the BAC group, TTF-1 was strongly expressed in 34 of 50 cases (68%) and was negative in 16 of 50 cases (32%), including 14 mucinous BACs. Although TTF-1 immunoreactivity was not statistically associated with good survival in BAC patients, those patients with strong immunohistochemical expression showed a trend toward longer survival. Our results indicate that TTF-1 positivity is an independent predictor of better survival, especially in patients with CA. Mucinous and nonmucinous BACs exhibit disparate staining patterns with TTF-1, with nonmucinous BAC demonstrating greater positivity. Although nonmucinous BAC patients showing strong positive staining had longer survival, the difference was not statistically significant, which is probably related to the overall good survival of patients with early-stage BAC.