title: Tumour markers for managing men who present with metastatic prostate cancer and serum prostate-specific antigen levels of <10 ng/mL.
abstract: OBJECTIVE
  To define immunohistochemical features of the primary cancers that might help in the differential diagnosis and monitoring of treatment in men presenting with metastatic prostate cancer and low serum levels of prostate-specific antigen (PSA), who can be difficult to diagnose and manage.
  
  
  METHODS
  Paraffin blocks of prostate biopsies were obtained for 33 patients presenting with untreated metastatic prostate cancer and serum PSA levels of <10 ng/mL. Sections were immunostained for PSA, prostatic acid phosphatase (PAP), prostate-specific membrane antigen (PSMA), androgen receptor (AR), chromogranin A and CD 56.
  
  
  RESULTS
  The combined Gleason scores were 8-10 in 25 men (76%) and 6 or 7 in the other eight (24%). Morphologically, there were no neuroendocrine features. PSA immunostaining was equivocal in 12 (36%) cases and in a further 19 (58%) was strong but focal and could be missed on biopsy sampling. PSMA was expressed in 90% of cases, and staining was widely distributed in nine of the 12 in which PSA staining was equivocal. There was strong AR expression in 30 (91%) cases and it was present in areas where PSA was absent.
  
  
  CONCLUSIONS
  In this patient group, immunohistochemical assessments of PSMA and AR are potentially useful as diagnostic markers.
authors.affiliation: The Prostate Cancer Research Centre, The Institute of Urology, London, UK.
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Birtle
authors.forename: Alex
authors.initials: A
authors.lastname: Freeman
authors.forename: John R W
authors.initials: JR
authors.lastname: Masters
authors.forename: Heather A
authors.initials: HA
authors.lastname: Payne
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Harland
mesh_terms: D000954:Antigens, Surface / Q000378:metabolism*; D001706:Biopsy / Q000379:methods; D043425:Glutamate Carboxypeptidase II / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis*
chemical_list: D000954:Antigens, Surface; C473848:FOLH1 protein, human; D043425:Glutamate Carboxypeptidase II; D017430:Prostate-Specific Antigen