Loss of p53 and Bcl-2 immunopositivity with time on stored slides of prostate and bladder cancer

Recently, publications have documented the loss of immunopositivity in Form alin-fixed, paraffin-embedded specimens stored on glass slides at room temp erature for up to 12 weeks. If a loss of immunostaining occurs with time, t his change needs to be defined. We examined whether immunostaining for p53 and Bcl-2 is lost in stored prostate and bladder cancer specimens. Tissue o btained by radical surgery that was known to stain positively for p53 and B cl-2 was sectioned, mounted on glass slides, and stored at room temperature for 0 to 12 weeks. Overall, 14 of the 15 samples stored for the full perio d showed staining loss. The mean number of positively stained cells decreas ed gradually with time for both markers. In two samples, this loss was suff iciently great that samples initially scored as immunopositive were conside red to be immunonegative at 12 weeks. Immunostaining is lost over time in a n unpredictable fashion in sections mounted on glass slides and stored at r oom temperature. The loss is not tissue, antibody, or antigen related and i s seen early as 2 weeks. Therefore, it is not advisable to assess p53 and B cl-2 expression on prostate and bladder cancer samples mounted on glass sli des and stored at room temperature for >2 weeks.