In the present analysis of gene expression profiles of ACC tumor samples, we found overexpression of polo-like kinase 1 (PLK-1), which is known to negatively regulate p53 activity, in 29 % of the tumors in our cohort and in 67 % of the tumors from the cohort published by Giordano, et al. [23]. This evidence concerns the gene PLK1 and neoplasm.