I have done IHC in lung sections with metastases and stained for a protein that I expect to be expressed in the cancer cells in the metastases. Despite that, the stain that I got was quite blurry (although I have done this protocol again for the same protein in tumor sections) and the stain was good. Apart from not getting signal in the expected area, I got some signal around the lung tissue that is not explained. I thought at first that there might me residual paraffin but I do 2 (5min washes in xylene). I am thinking of doing the staining again with a negative control (no addition of first antibody) in order to see why it stains in non-specific regions. Regarding the blurry image, what can be the reason for that ? Do you have any suggestions for resolving these issues? Thank you very much in advance!