Test Catalog

Test ID: HMB45    
HMB45 Immunostain, Technical Component Only

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

Identification of activated and neoplastic melanocytes

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

The HMB45 immunostain identifies an antigen that is associated with a premelanosomal glycoprotein found in activated and neoplastic melanocytes. Most melanomas (approximately 90%) react with HMB45. HMB45 staining is cytoplasmic and is usually diffuse but may be focal. Benign nevi (moles) and other tumors that have melanin production (such as peripheral nerve sheath tumors) also stain positively.

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. Uguen A, Uguen M, Gujbourg B, Talagas M, Marcorelles P, De Braekeleer M: The p16-Ki-67-HMB45 immunohistochemistry scoring system is highly concordant with the fluorescent in situ hybridization test to differentiate between melanocytic nevi and melanomas. Appl Immunohistochem Mol Morphol. 2018 Jul;26(6):361-367. doi: 10.1097/PAI.0000000000000428

2. Kriegsmann M, Kriegsmann M, Kriegsmann K, et al: Expression of HMB45, melanA and SOX10 is rare in non-small cell lung cancer. Diagn Pathol. 2018 Sep 11;13(1):68. doi: 10.1186/s13000-018-0751-7

3. Garola R, Singh V: Utility of p16-Ki-67-HMB45 score in sorting benign from malignant Spitz tumors. Pathol Res Pract. 2019 Oct;215(10):152550. doi: 10.1016/j.prp.2019.152550