Editing Prostate-specific antigen (section)

==Sources==

PSA is produced in the [[epithelium|epithelial]] cells of the prostate, and can be demonstrated in biopsy samples or other [[histology|histological]] specimens using [[immunohistochemistry]]. Disruption of this epithelium, for example in inflammation or [[benign prostatic hyperplasia]], may lead to some diffusion of the antigen into the tissue around the epithelium, and is the cause of elevated blood levels of PSA in these conditions.<ref name="Leong-2003">{{cite book | vauthors = Leong AS, Cooper K, Leong FJ | year = 2003 | title = Manual of Diagnostic Cytology | edition = 2nd | publisher = Greenwich Medical Media, Ltd. | pages = 79–80 | isbn = 978-1-84110-100-2 }}</ref>

More significantly, PSA remains present in prostate cells after they become malignant. Prostate cancer cells generally have variable or weak staining for PSA, due to the disruption of their normal functioning. Thus, individual prostate cancer cells produce less PSA than healthy cells; the raised serum levels in prostate cancer patients is due to the greatly increased number of such cells, not their individual activity. In most cases of prostate cancer, though, the cells remain positive for the antigen, which can then be used to identify [[metastasis]]. Since some high-grade prostate cancers may be entirely negative for PSA, however, histological analysis to identify such cases usually uses PSA in combination with other antibodies, such as [[prostatic acid phosphatase]] and ''[[CD57]]''.<ref name="Leong-2003"/>