Anticytokeratin antibody 34 beta E12 staining in prostate carcinoma

Anticytokeratin antibody 34 beta E12 is advocated as an immunohistochemical stain for discriminating benign and malignant lesions of the prostate. Positive staining with 34 beta E12 is said to identify benign lesions, whereas negative staining is said to help substantiate a diagnosis of carcinoma. It is further claimed that 34 beta E12 does not stain prostate carcinoma. The studies leading to these conclusions used hematoxylin-eosin-stained sections of primary prostate lesions as controls. Although the cytokeratin content of a few cell lines of metastatic prostate carcinoma has been investigated, the 34 beta E12 immunohistochemical staining of metastatic prostate carcinoma has not been evaluated. If 34 beta E12 positivity is present only in benign prostate cells, then metastatic prostate carcinoma cells should be uniformly negative with this stain. In 14 cases of moderate and high-grade prostate cancer with metastases to lymph nodes, we found 34 beta E12 positivity in 6 (43%) of 14 metastases and in 7 (54%) of 13 primary tumors. Our findings of 34 beta E12 staining in primary and metastatic moderately and poorly differentiated prostate carcinoma differ from those reported in the literature for well-differentiated prostate carcinoma. We urge caution in the use and interpretation of 34 beta E12 staining for the diagnosis of primary and metastatic prostate carcinoma.