Steam heat with an EDTA buffer and protease digestion optimizes immunohistochemical expression of basal cell-specific antikeratin 34 beta E12 to discriminate cancer in prostatic epithelium

In select cases of prostatic carcinoma, antikeratin 34 beta E12 immunohisto chemical analysis is diagnostically useful for specific labeling of basal c ells. This antibody, however, is prone to variability in staining, and the optimal conditions were not, to our knowledge, previously defined. We combi ned steam heat with EDTA buffer (steam-EDTA) and protease digestion (steam- EDTA + protease) to optimize epitope retrieval of antikeratin 34 beta E12 i n 42 cases of prostatic cancer, Results were judged by the percentage of ce lls staining and by staining intensity. In benign epithelium, steam-EDTA protease significantly increased the percentage of immunoreactive cells (fr om 74 to 93%) and the intensity of staining (from 2.1 to 3.0 on a scale of 0-3+) by comparison with protease alone (all P <.001). In high-grade prosta tic intraepithelial neoplasia, the percentage of cells staining increased f rom 55 to 73% and intensity increased from 1.7 to 2.8 (both P <.001). Steam -EDTA + protease also minimized variability in results between cases, with essentially no background stromal staining. Cancer was negative in all of o ur cases by both methods. We conclude that steam-EDTA + protease significan tly enhances basal cell immunoreactivity compared with protease treatment a lone in noncancerous prostatic epithelium. This helps to prevent misinterpr etation of histologic mimics of cancer, such as atrophic acini and high-gra de prostatic intraepithelial neoplasia, that result from false-negative sta ining.