Prostatic cancer presenting as metastatic adenocarcinoma of undetermined origin. Immunodiagnosis by prostatic acid phosphatase.

Adenocarcinoma of the prostate may occasionally present as distant metastatic disease. This tumor, if accurately identified, is amendable to effective treatment with hormonal manipulations. We have seen nine patients with prostatic cancer presenting as metastatic adenocarcinoma of undetermined origin: two presented with involvement in the lung and the mediastinum, five with left supraclavicular lymphadenopathy and two with known prostatic cancer with stable disease presented with supraclavicular lymphadenopathy. By employing an immunoperoxidase technique using prostatic acid phosphatase as the marker for the prostatic cells, we demonstrated the presence of the prostatic enzyme antigen in the paraffin embedded tissues from the metastatic tumor. This finding directed further investigation of the prostate gland leading to the discovery of the primary tumor in all nine patients. It may be beneficial to use this technique in all male patients with adenocarcinoma of undetermined primary site.