Tissue microarrays are reliable tools for the clinicopathological characterization of lung cancer tissue.

Background: The advantage of tissue microarray (TMA) is its ability to efficiently analyze large numbers of tissue specimens in a methodologically uniform way. The reliability of TMAs, especially with regard to clinicopathological characterizations, when compared to conventional immunohistochemistry (IHC) was evaluated. Materials and Methods: Seventy-two embedded tissue sections from lung cancer specimens were stained with monoclonal antibodies against the tumor-associated markers TA-MUC1 and Lewis Y. Three representative cores of every tumor were embedded in a paraffin array multiblock. The IHC was evaluated by the immunoreactive score (IRS). Results: The data for the TMA IHC and the conventional IHC were concordant (kappa ≥80% ) for both markers. Likewise, discordance (McNemar's test) was low, and sensitivity and specificity were above 80% for both markers. In the samples with high positive expression, the concordance increased (kappa ≥90% ), discordance disappeared (McNemar p=1.0), and sensitivity and specificity increased above 90% for both markers. Using Cox regression models, all the clinicopathological dependencies were equivalent for both techniques and both markers. Conclusion: Immuno- histochemistry with tissue microarrays is valid and provides results equivalent to conventional immunohistochemistry with respect to expression patterns and clinicopathological characterizations. At present, lung cancer is the leading cause of cancer-related death in both sexes in the U.S. (22), with an average overall survival rate of less than 15% (35). Unfortunately, this situation is not expected to change within the next decades, although most cases could be avoided (1) as lung cancer pathogenesis is dramatically influenced by exposure to tobacco smoke (36). Given its poor prognosis and its high incidence, emphasis should be put on earlier diagnosis and improved therapeutic options. Referring to this, the use of the tissue microarray (TMA) technology for immunohisto- chemical (IHC) purposes appears to be an advantageous development, as it assures the homogeneous and synchronous analysis of different tissue samples and their gene expression patterns under equivalent test conditions (24, 30, 42). As shown by Kononen et al., this technique allows the