The potential explanations may account for this discrepancy include: (i) The tumor may still produce PSA at levels sufficient to be detected in the serum, but below the threshold for IHC detection in tissue sections, and (ii) There may be a minor component of acinar-type adenocarcinoma mixed with ductal carcinoma [1,4]. This evidence concerns the gene KLK3 and breast ductal adenocarcinoma.