Prostate-specific antigen

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Prostate-specific antigen, abbreviated PSA, is marker that is quite specific for the prostate.

Micrograph showing a PSA immunostain marking prostate carcinoma.

General

  • Quantity in the serum used to screen for prostate cancer and follow patients with a history of prostate cancer.
  • PSA immunostain useful for classifying a carcinoma as prostate carcinoma.

Serum PSA

Age-normal:

  • 40s - 2.5 ng/ml.
  • 50s - 3.5 ng/ml.
  • 60s - 4.5 ng/ml.
  • 70s - 6.5 ng/ml.

Note:

  • The units for PSA may also be μg/L; note that 1 μg/L = 1 ng/ml.

Prostate-specific antigen density

Abbreviated PSAD.

Normal is often considered to be: <0.15 ng/ml2.

  • Approximately 8% of individuals below the cut-point (0.15 ng/ml) have medium or high-grade cancer.[3]
  • In another series, 48% of individuals with cancer had a PSAD >0.15 ng/ml2.[4]
  • Differences between races have been noted in one study; in those without prostate cancer:[1]
    • 0.19 +/- 0.03 ng/ml2 (blacks).
    • 0.11 +/- 0.01 ng/ml2 (whites).

PSAD is a better predictor than (unadjusted) serum PSA for:

A forumla for PSAD

Benson et al.:[6]

 

Where:

 .[8]
H, W, L are the height, width and length.

An alternate estimation of the volume is:

 .
D1, D2, D3 are the major axes.

Notes:

  • The volume of an ellipsoid is:
 .
  • As 1 cm3 is equal to 1 ml, the units of PSAD are (ng/ml)/cm3 or ng/ml2.

Immunostain

  • Relatively specific for prostate
  • May be found in normal pancreatic, salivary gland, Skene's glands and lactating breast tissue.
  • In women, positive in up to 30-40% of breast cancers and also in tubulo-squamous polyps of the vagina.

Microscopic

Features - PSA immunostain:

  • Granular cytoplasmic staining.

Notes:

  • May be very weak -- need to look at high power.

See also

References

  1. 1.0 1.1 1.2 Henderson, RJ.; Eastham, JA.; Culkin, DJ.; Kattan, MW.; Whatley, T.; Mata, J.; Venable, D.; Sartor, O. (Jan 1997). "Prostate-specific antigen (PSA) and PSA density: racial differences in men without prostate cancer.". J Natl Cancer Inst 89 (2): 134-8. PMID 8998182.
  2. Ku JH, Ahn JO, Lee CH, et al. (September 2002). "Distribution of serum prostate-specific antigen in healthy Korean men: influence of ethnicity". Urology 60 (3): 475–9. PMID 12350489.
  3. Boulos, MT.; Rifkin, MD.; Ross, J. (Sep 2001). "Should prostate-specific antigen or prostate-specific antigen density be used as the determining factor when deciding which prostates should undergo biopsy during prostate ultrasound.". Ultrasound Q 17 (3): 177-80. PMID 12973074.
  4. Aganovic, D.; Prcic, A.; Kulovac, B.; Hadziosmanovic, O. (2012). "Influence of the prostate volume, prostate specific antigen density and number of biopsy samples on prostate cancer detection.". Med Arh 66 (1): 41-4. PMID 22482342.
  5. Sfoungaristos S, Katafigiotis I, Perimenis P (2013). "The role of PSA density to predict a pathological tumour upgrade between needle biopsy and radical prostatectomy for low risk clinical prostate cancer in the modified Gleason system era". Can Urol Assoc J 7 (11-12): E722–7. doi:10.5489/cuaj.374. PMC 3840515. PMID 24282465. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3840515/.
  6. 6.0 6.1 Benson MC, Whang IS, Pantuck A, et al. (March 1992). "Prostate specific antigen density: a means of distinguishing benign prostatic hypertrophy and prostate cancer". J. Urol. 147 (3 Pt 2): 815–6. PMID 1371554.
  7. Verma A, St Onge J, Dhillon K, Chorneyko A (June 2014). "PSA density improves prediction of prostate cancer". Can J Urol 21 (3): 7312–21. PMID 24978363.
  8. Eri, LM.; Thomassen, H.; Brennhovd, B.; Håheim, LL. (2002). "Accuracy and repeatability of prostate volume measurements by transrectal ultrasound.". Prostate Cancer Prostatic Dis 5 (4): 273-8. doi:10.1038/sj.pcan.4500568. PMID 12627211.