Objective: To study the expression and clinical significance of cytokeratin subtypes CK7 and CK20 and thyroid transcription factor-1 (TTF-1) in bronchioloalveolar carcinoma (BAC), and to investigate the value of these factors in identification of the prognosis of BAC.
Methods: Eighty-one specimens of BAC resected during operation, 68 of non-mucinous type and 13 of mucinous type, underwent immunohistochemical examination to detect the expression of CK7, CK20, and TTF-1. The value of these 3 factors in the identification of the prognosis of BAC was examined by survival analysis.
Results: All specimens showed positive expression of CK7, CK20, and TTF-1. There was no significant differences in CK7 expression rate among different ages, clinical stages, and pathological subtypes (all P > 0.05). Compared with that in the BAC of stage III and that of BAC of non-mucinous type, the CK20 positive rates of the BAC of stage I - II and mucinous type were both significantly higher (chi(2) = 3.928, P < 0.05, and chi(2) = 11.512, P < 0.05). The TTF-1 positive rates of the BAC of stage III and nonmucinous type were significantly higher than those of stage I - II and mucinous type respectively (chi(2) = 7.840, P < 0.05, and chi(2) = 19.497, P < 0.05). There was a statistically significant positive correlation between the expression of CK7 and expression of TTF-1 (r = 0.257, P = 0.021). Univariate analysis showed that the main prognostic factors were TTF-1 expression (P = 0.017), clinical stage (P = 0.000), tumor diameter (P = 0.017) and N stage (P = 0.000). Strata analysis suggested that in the nonmucinous type BAC patients the survival time of those positive for TTF-1 expression was superior to those negative for TTF-1 (P = 0.009); and in the stage III BAC patients the survival time of those positive for TTF-1 was superior to those negative for TTF-1 (P = 0.022). Cox regression analysis suggested that TTF-1 (P = 0.035), TNM stage (P = 0.000), tumor diameter (P = 0.034), and N stage (P = 0.000) were independent factors affecting the prognosis.
Conclusion: There is a statistically significant positive correlation between the expression of CK7 and the expression of TTF-1. TTF-1 and CK20 provide a new evidence for the molecular staging of BAC. TTF-1, TNM stage, tumor diameter and N stage are all independent factors affecting the prognosis of BAC.