Immunostaining by dual tumor tissue paraffin blocks increases the sensitivity of c-Met detection in gastric cancer

Background: Gastric cancer (GC) is the second most frequent cause of cancer deaths worldwide. c-Met, a receptor tyrosine kinase, transduces signals from extracellular growth factors. c-Met-targeted therapeutics hold a great potential in treating gastric and related cancers, and a precise evaluation of c-Met expression is a prerequisite for subsequent treatment. Methods: We compared the sensitivity between one and two paraffin blocks in evaluating c-Met expression in GC subjects by immunohistochemistry (IHC). A total of 365 GC patients were divided into cohort 1 (n = 206) for the one tumor tissue paraffin block test and cohort 2 (n = 159) for the dual tumor tissue paraffin block test. In the dual blocks group, we investigated the results from two different paraffin blocks, then we used the higher one as the final score. Results: Inconsistent c-Met expression in the dual paraffin blocks group occurred in 29 (18.2%) cases. The pooled data in cohort 1 and cohort 2 indicate that when using results from dual paraffin blocks, the c-Met positive (3+) rate of GC testing could be promoted. Conclusion: In GC, using dual tumor tissue paraffin blocks instead of one tumor tissue paraffin block is an efficient, economical and practical method of minimizing the false-negative rate of c-Met status assessment by IHC.