Revisiting ALK (D5F3) immunohistochemistry: Insights into focal staining and neuroendocrine differentiation.

This study demonstrates that strong but focal ALK (D5F3) immunostaining and strong expression in neuroendocrine differentiation may not indicate ALK fusion. By considering these findings, we can improve the accuracy of patient selection for targeted therapy by minimizing false-positive interpretations of ALK (D5F3) staining.