Prostatic acid phosphatase

Last revised by Joachim Feger on 11 Feb 2022

Prostatic acid phosphatase (PAP) also known as prostatic specific acid phosphatase (PSAP) is an enzyme generated by prostatic glandular tissue.


It can be used in immunohistochemistry to identify prostatic tissue including prostatic epithelium and prostatic ducts and is usually expressed in prostate cancer 1.

It has been used as a serum marker and high values correlate with a high Gleason grade but it is less sensitive than prostate-specific antigen (PSA) 1,2. It might become negative after androgen deprivation therapy.

Research is conducted for its suitability as an immunotherapy target 1,3.

It might be also positive in other cancers including bladder adenocarcinoma, rectal carcinoids or salivary gland tumors and diverse nonprostatic diseases such as Paget disease, hyperparathyroidism, multiple myeloma etc. 2.

History and etymology

Prostatic acid phosphatase (PAP) was the first clinically useful tumor marker after its first description by AB Gutman and EB Gutman in 1938 4. After the appearance of prostate-specific antigen (PSA) in the 1980s its use as a serum marker has declined considerably.

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