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Immunohistochemistry (IHC)
Test Description

PD-L1 IHC 22C3 pharmDx is a qualitative immunohistochemical assay using Monoclonal Mouse Anti-PD-L1, Clone 22C3 intended for use in the detection of PD-L1 protein in formalin-fixed, paraffin-embedded (FFPE) triple-negative breast cancer (TNBC) tissue using EnVision FLEX visualization system on Autostainer Link 48. This test is indicated as an aid in identifying TNBC patients for treatment with KEYTRUDA® (pembrolizumab). Tissues with PD-L1 Combined Positive Score (CPS) ≥ 10 are considered positive.

Stain-only (tech-only) testing is available to clients who have completed the test kit manufacturer’s online interpretation training.

All PD-L1 IHC test options may be viewed here.

Clinical Significance

PD-L1 22C3 FDA (KEYTRUDA®) for TNBC is a companion diagnostic (CDx) for certain triple-negative breast cancer patients. PD-L1 expression with ≥10% Combined Positive Score (CPS) may be associated with increased progression-free survival in patients with metastatic or advanced, locally unresectable TNBC treated with KEYTRUDA® and chemotherapy.

Specimen Requirements
  • A formalin-fixed, paraffin-embedded (FFPE) tissue block is preferred specimen type
  • One (1) unbaked, unstained slide for H&E staining (required) and two to three (2-3) positively charged unstained slides (all cut at 4-5 microns) for each test/antibody ordered
  • Block and slide identifiers should be clearly written and match exactly with the specimen ID and specimen labeling as noted on the requisition.
Storage and Transportation

Use cold pack for transport. Make sure cold pack is not in direct contact with specimen.

CPT Code(s)*
New York Approved
Level of Service
Turnaround Time

Global: 48 hours, Tech-Only (stain only): 24 hours

  1. PD-L1 IHC 22C3 pharmDx [package insert]. Carpinteria, CA: Dako; PT0020/Rev F.
  2. KEYTRUDA® (pembrolizumab) [package insert]. Whitehouse Station, NJ: Merck & Co., Inc; usmg-mk3475-iv-2011r036

*The CPT codes provided with our test descriptions are based on AMA guidelines and are for informational purposes only. Correct CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed.