Figure 4  Immunohistochemistry of CDKN2A in primary tumors. (A) Bladder tumor control minus primary antibody. Some nonspecific stromal staining is visible in the stroma. (B) Strong specific cytoplasmic and nuclear staining in a bladder positive control in presence of primary antibody. (C) Results from representative tumors show very low cytoplasmic staining of CDKN2A from a tumor with a large homozygous deletion of CDKN2A. (D) Strong nuclear and cytoplasmic staining of CDKN2A and unstained normal stromal cells from a tumor which retained 2 copies of CDKN2A. Scale bar = 25 μm.