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Prostatic acid phosphatase (PAP, PSAP)

Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 17 April 2012, last major update April 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.


● Prostatic acid phosphatase (PAP), also prostatic specific acid phosphatase (PSAP), is enzyme produced by prostate tissue
● Acid phosphatases release phosphate groups, optimally at acid pH
● May promote HIV infection; naturally occurring fragments form amyloid fibrils (Semen-derived Enhancer of Virus Infection), capture HIV virions and promote their attachment to target cells (Cell 2007;131:1059)

Uses for pathologists

● Identifies prostatic origin of metastases (whose primary is PAP+), including bone metastases (Ann NY Acad Sci 2011;1237)
● Differentiates between prostatic and urothelial carcinomas
● Differentiates between prostatic adenocarcinoma and mesonephric remnant hyperplasia (Ann Diagn Pathol 2009;13:402)
● Presence is presumptive test for semen in forensic studies

Micro images

Prostate-normal (figure D)

Various tissues (normal prostate and carcinoma)

Primary (left), metastasis to lymph node (middle), metastasis to soft tissue (right) of prostatic adenocarcinoma (figure D in all images)

Prostatic adenocarcinoma (figure D of both images); right image is seminal vesicle invasion

Prostatic adenocarcinoma metastatic to breast (figure C)

Prostatic duct carcinoma

Prostate / colon: in situ hybridization

Rectal neuroendocrine tumour shows diffuse and intense immunoreactivity for prostatic acid phosphatase.

Seminal vesicle-normal is PAP negative (figure D)

Positive staining - normal

● Prostatic epithelium (lysosomal granules) and prostatic ducts
● May be expressed in non-prostatic tissue, but at 1-2 orders of magnitude less than in prostate (Int J Clin Exp Pathol 2011;4:295)

Positive staining - disease

● Prostatic adenocarcinoma and duct carcinoma (considered more sensitive but less specific than PSA)
● PSA/PAP less sensitive in poorly differentiated adenocarcinoma (Am J Surg Pathol 1986;10:765, Am J Surg Pathol 1982;6:553)
● PSA/PAP may become negative after hormonal treatment (Hum Pathol 1996;27:1377)
● Bladder adenocarcinomas and rectal carcinomas may be strongly PAP+ but are PSA-
● Bladder cystitis cystica / cystitis glandularis is occasionally positive (Arch Pathol Lab Med 1988;112:734)
● Rectal carcinoids also positive for PAP, perhaps due to shared cloacal derivation of rectum and prostate (Am J Surg Pathol 1991;15:785); also ovarian strumal carcinoids
● Salivary gland: pleomorphic adenoma (50%), duct carcinoma (20%)

Negative staining

● Prostatic basal cells, urothelium, inflammatory cells
● Nephrogenic adenoma of prostate, bladder, kidney (usually, may be weakly positive)
● Mesonephric remnant hyperplasia (Ann Diagn Pathol 2009;13:402)
● Prostatic clear cell adenocarcinoma
● Non-prostate tissue and tumors other than those indicated above are usually negative / weak

End of Stains > Prostatic acid phosphatase (PAP)

Ref Updated: 3/30/12

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