We developed an IHC protocol for assessing expression of PHLDA1 and performed IHC staining of whole tissue sections on 24 primary breast cancer cases including 12 ErbB2 positive and 12 ErbB2 negative breast adenocarcinomas tested by SISH study and used available normal mammary tissues on the same slides as the internal normal control. The gene discussed is ERBB2; the disease is breast adenocarcinoma.