It was discovered that prostate-specific antigen is produced by non-prostatic endocrine cancers. It was further discovered that non-prostatic endocrine cancers with steroid receptors can be stimulated with steroids to cause them to produce PSA either initially or at increased levels. This invention relates to the imaging of non-prostatic endocrine cancers by labelled biological binding units which bind to prostate-specific antigen in an imaging procedure, such as, radio imaging or magnetic resonance imaging. Further, the PSA-binding units may be constructed to deliver a toxic agent, such as a radioisotope, toxin or a drug to provide endocrine cancer therapy. Another aspect of the invention is passive immunotherapy against endocrine cancers by treatment with PSA-binding units.