Test Catalog

Test ID: CD56    
CD56 Immunostain, Technical Component Only

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

Aiding in the identification of tumors with neuroendocrine differentiation


Aiding in the identification of natural killer cell lineage in a subset of lymphomas

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

CD56 is an adhesion molecule mediating homophilic and heterophilic adhesion in neurons, natural killer cells, and a small subset of CD4- and CD8-positive T cells. It is expressed in tumors with neuroendocrine differentiation (small cell lung carcinoma and neural-derived tumors) or natural killer cell lineage (subset of lymphomas). In normal small intestine, the ganglion cells in the muscle wall and nerves will show strong staining. Scattered lymphocytes may also be positive.

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. 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. Kerekes D, Visscher DW, Hoskin TL, et al: CD56+ immune cell infiltration and MICA are decreased in breast lobules with fibrocystic changes. Breast Cancer Res Treat. 2018;167(3):649-658. doi: 10.1007/s10549-017-4558-0

2. Skaria PE, Ahmed AA, Yin H, Nicol K, Reid KJ, Singh V: Expression of HBME-1 and CD56 in follicular variant of papillary carcinoma in children: An immunohistochemical study and their diagnostic utility. Pathol Res Pract. 2019;215(5):880-884. doi: 10.1016/j.prp.2019.01.031

3. Moritz AW, Schlumbrecht MP, Nadji M, Pinto A: Expression of neuroendocrine markers in non-neuroendocrine endometrial carcinomas. Pathology. 2019;51(4):369-374. doi:10.1016/j.pathol.2019.02.003

4. Alshenawy HA: Utility of immunohistochemical markers in diagnosis of follicular cell derived thyroid lesions. Pathol Oncol Res. 2014;20(4):819-828. doi: 10.1007/s12253-014-9760-3