Test Catalog

Test ID: KRT34    
Keratin (34BE12) Immunostain, Technical Component Only

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

Identification of cells expressing high-molecular-weight cytokeratin

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

For the initial technical component only immunohistochemical (IHC) stain performed, the appropriate bill-only test ID will be reflexed and charged (IHTOI). For each additional technical component only IHC stain performed, an additional bill-only test ID will be reflexed and charged (IHTOA).

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

Keratin 34 beta E12 (sometimes referred to as Keratin 903) is a monoclonal antibody that reacts with high-molecular-weight cytokeratin. In normal prostate, reactivity for keratin 34BE12 can be seen in the basal layer of prostatic glands in a membranous/cytoplasmic pattern. It is most useful as a basal cell-specific marker in the prostate, and shows loss of staining around glands of prostate cancer, which do not have a basal cell layer.

Interpretation Provides information to assist in interpretation of the test results

This test does not include pathologist interpretation: only technical performance of the stain. If interpretation is required, order PATHC / Pathology Consultation for a full diagnostic evaluation or second opinion of the case.


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; call 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. Brimo F, Epstein JI: Immunohistochemical pitfalls in prostate pathology. Hum Pathol. 2012 Mar;43(3):313-324

2. Hameed O, Humphrey PA: Immunohistochemistry in the diagnosis of minimal prostate cancer. Current Diagn Pathol. 2006 Aug;12(4):279-291
3. Martens MB, Keller JH: Routine immunohistochemical staining for high-molecular weight cytokeratin 34-beta and alpha-methylacyl CoA racemase (P504S) in postirradiation prostate biopsies. Mod Pathol. 2006 Feb;19(2):287-290
4. Varma M, Morgan M, Amin MB, Wozniak S, Jasani B: High molecular weight cytokeratin antibody (clone 34beta12): a sensitive marker for differentiation of high-grade invasive urothelial carcinoma from prostate cancer. Histopathology. 2003 Feb;4292):167-172