Test Catalog

Test ID: PACPI    
Prostatic Acid Phosphatase (PACP) Immunostain, Technical Component Only

Useful For Suggests clinical disorders or settings where the test may be helpful

Enzyme produced in normal prostatic epithelium and prostatic adenocarcinoma

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Prostatic acid phosphatase (PACP) is a cytoplasmic enzyme produced in normal prostatic epithelium and prostatic adenocarcinoma. PACP is a useful adjunct to the immunostain for prostate-specific antigen; if 1 of these 2 markers is immunoreactive, a tumor of prostatic origin is likely. Bladder epithelium and certain neuroendocrine tumors such as rectal carcinoid may be weakly immunoreactive.

Interpretation Provides information to assist in interpretation of the test results

This test includes only technical performance of the stain (no pathologist interpretation is performed). Mayo Clinic cannot provide an interpretation of tech only stains outside the context of a pathology consultation. If an interpretation is needed, refer to PATHC / Pathology Consultation for a full diagnostic evaluation or second opinion of the case. All material associated with the case is required. Additional specific stains may be requested as part of the pathology consultation, and will be performed as necessary at the discretion of the Mayo pathologist.


The positive and negative controls are verified as showing appropriate immunoreactivity and documentation is retained at Mayo Clinic Rochester. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request. Contact 855-516-8404.


Interpretation of this test should be performed in the context of the patient's clinical history and other diagnostic tests by a qualified pathologist.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Age of a cut paraffin section can affect immunoreactivity. Stability thresholds vary widely among published literature and are antigen-dependent. Best practice is for paraffin sections to be cut within 6 weeks.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1.Hameed O, Humphrey PA: Immunohistochemistry in diagnostic surgical pathology of the prostate. Semin Diagn Pathol 2005;22(1):88-104

2. Hammerich KH, Ayala GE, Wheeler TM: Application of immunohistochemistry to the genitourinary system (prostate, urinary bladder, testis, and kidney). Arch Pathol Lab Med 2008;132:432-440

3. Varma M, Berney DM, Rhodes A: Technical variations in prostatic immunohistochemistry: Need for standardisation and stringent quality assurance in PSA and PSAP immunostaining. J Clin Pathol 2004;57:687-690