Immunohistochemical detection of prostate specific antigen (PSA) is an
important adjunct for the pathologist. The primary diagnostic uses of
PSA immunohistochemistry include: separation of prostatic adenocarcin
omas from other primary adenocarcinomas located in the pelvis; determi
nation of the site of origin of a metastatic adenocarcinoma; and deter
mination of whether an adenocarcinoma in a distant organ represents a
metastasis from a prostate primary, A variety of polyclonal and monocl
onal antibodies are available which may be used to detect PSA in a var
iety of specimens, including formalin-fixed, paraffin-embedded section
s, PSA is strongly expressed in the cytoplasm of normal and hyperplast
ic prostate glandular epithelium. Similarly, PSA expression is retaine
d by the vast majority of prostatic adenocarcinomas, although the quan
tity and quality of staining are decreased, In general, comparatively
few extra prostatic tissues and neoplasms have been shown to express P
SA, supporting the high specificity of this marker.