Immunohistochemical analysis of SOX9 expression in normal lung tissue and primary NSCLC. A, thin sections of paraffin-embedded specimens of a total of 2 normal lung tissues and 142 primary NSCLC specimens including AJCC grade I to IV NSCLC samples were stained by immunohistochemistry using an anti-SOX9 antibody. a and b, normal lung tissue; c and d, AJCC grade I NSCLC; e and f, AJCC grade II NSCLC; g and h, AJCC grade III NSCLC; i and j, AJCC grade IV. Amplification, 200 (a, c, e, g, and i) and 400 (b, d, f, h and j). Immunohistochemical analyses were done two independent times on each of the samples with similar results. B, statistical quantification of the average mean absorbance of SOX9 staining between normal lung tissues (4 cases) and NSCLC specimens of different AJCC grades (30 random cases per grade). Average mean absorbance of SOX9 staining increases as NSCLC progresses to higher grades. *, P < 0.01.