PD‑L1 22C3 IHC with Combined Positive Score (CPS) Interpretation, pembrolizumab (KEYTRUDA)
Also known as: 22C3 GAST
Use
This immunohistochemistry (IHC) test evaluates PD‑L1 protein expression using the 22C3 antibody clone to aid in patient selection for pembrolizumab (KEYTRUDA) therapy. Tumor proportion score (TPS) interpretation is provided for non‑small cell lung cancer (NSCLC), while combined positive score (CPS) interpretation is provided for gastric, esophageal/GEJ adenocarcinoma, cervical carcinoma, head and neck squamous carcinoma, and triple‑negative breast cancer. The scoring method is determined by ARUP based on the pathology report. Other tumor types are reported with TPS plus an off‑label disclaimer. These scores help predict response to pembrolizumab and, for NSCLC, also to cemiplimab (LIBTAYO).
Special Instructions
Refer to ARUP test 3017615 as of May 20, 2024; ARUP medical director chooses scoring type based on pathology report. For multiple specimens, indicate “choose best block” or submit separate orders; a pathologist block selection fee (test code 3002076) applies if unspecified. Include surgical pathology report and tissue site. Use ARUP tissue transport kit #47808, available via ARUP Connect or Client Services.
Limitations
At least 100 viable tumor cells are required for interpretation. Slides that have been oven‑baked, or specimens decalcified or fixed in fixatives other than 10% neutral buffered formalin are not validated and should be interpreted with caution. Specimens with fewer than 100 viable tumor cells, decalcified tissue, blocks with no tumor remaining, or fixed in non‑NBF fixatives are unacceptable.
New York Approved
Methodology
Immunoassay (IHC)
Biomarkers
LOINC Codes
- 94736‑6
- 31208‑2
- 83052‑1
Result Turnaround Time
3-7 days
Related Documents
For more information, please review the documents below
Specimen
Tissue (FFPE)
Volume
Not provided
Minimum Volume
Not provided
Container
tissue block or 5 unstained positively charged slides (3‑5 µm thick)
Collection Instructions
Send tumor tissue as formalin‑fixed, paraffin‑embedded block or at least 5 unstained charged slides; use ARUP tissue transport kit #47808
Storage Instructions
Protect from excessive heat; ship in cooled container in summer months
Causes for Rejection
Fewer than 100 viable tumor cells; non‑10% NBF fixative; decalcified specimens; oven‑baked slides; blocks with no tumor
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | block: ambient indefinitely; slides: ambient varies by type (e.g. NSCLC slides ambient 6 months; gastric/GEJ 5 months; ESCC 1 month; cervical 1 month; HNSCC 4 months; TNBC 4 months) |
| Refrigerated | block: indefinitely; slides: refrigerated varies (NSCLC 6 months; gastric/GEJ 5 months; ESCC 4.5 months; cervical 5 months; HNSCC 6 months; TNBC 7.5 months) |
| Frozen | Unacceptable |