ALK immunohistochemical staining.

<p>A, no staining (score, 0); B, faint staining (score, 1+); C, moderate staining (score, 2+); D, strong staining (score, 3+); E, ALK protein staining of patient with concurrent ALK and EGFR mutation (patient 1, score, 1+); F, ALK protein staining of patient with concurrent ALK and EGFR mutation (patient 2, score, 2+). Magnification, 400×.