Immunoperoxidase staining for p53 protein: the positive population shows intense brown nuclear staining. (A) Cytospin of CLL lymphocytes: the immunostaining shows the coexistence of p53-positive and p53-negative cells within the same leukemic population. (B) Cytospin containing a mixture of Raji cells (p53 positive) and normal peripheral blood lymphocytes (p53 negative) used as control.