Immunohistochemistry is one of the most valuable services a pathology group bills, and one of the most audited. The codes are counted per specimen and per antibody, so a single case can generate several lines, and every extra unit has to be supported. This guide explains CPT 88342, its add-on 88341, the multiplex code 88344, and how to count units without triggering denials. It builds on our pathology CPT codes guide.
Quick answer: Bill CPT 88342 once per specimen for the first single-antibody IHC stain. Bill add-on 88341 for each additional single-antibody stain on that same specimen, and 88344 for each multiplex stain. When a stain is quantified with morphometric analysis (88360 or 88361), do not also bill 88342 for the same antibody on that specimen.
Key takeaways
- Per specimen: 88342 is reported once for each separately identified specimen.
- Add-on for extra antibodies: 88341 covers each additional single antibody on the same specimen.
- Multiplex is separate: 88344 is per multiplex stain procedure per specimen.
- No double counting: Quantitative 88360/88361 replaces 88342 for that antibody.
What Is CPT 88342?
CPT 88342 reports immunohistochemistry or immunocytochemistry, per specimen, for the initial single antibody stain procedure. It covers the stain and its interpretation for qualitative or semi-quantitative results.
The IHC code family
| CPT | What it reports | How to count |
|---|---|---|
| 88342 | Initial single antibody stain procedure | Once per specimen |
| 88341 | Each additional single antibody stain procedure (add-on) | Per additional antibody, same specimen |
| 88344 | Each multiplex antibody stain procedure | Per multiplex stain, per specimen |
| 88360 | Morphometric analysis, tumor marker, manual | Per specimen, per marker |
| 88361 | Morphometric analysis, tumor marker, computer-assisted | Per specimen, per marker |
How to Count 88342 and 88341 Units
| Scenario | How to report |
|---|---|
| One specimen, one antibody | 88342 x 1 |
| One specimen, four antibodies | 88342 x 1, 88341 x 3 |
| Two specimens, two antibodies each | 88342 x 2, 88341 x 2 |
| One specimen, one multiplex stain | 88344 x 1 |
| One specimen, HER2 quantified by image analysis | 88361 x 1 for HER2; do not add 88342 for HER2 |
What is a specimen? Each separately identified and submitted tissue sample, the same unit used for surgical pathology codes such as 88305. Multiple blocks or slides from one specimen are still one specimen.
Billing 88342 for a control slide, or counting each slide instead of each antibody, is a common overbilling pattern. Payers also set daily unit limits for these codes. Check the CMS NCCI edits and MUE tables before submitting high unit counts.
Modifiers for IHC Billing
| Modifier | When to use it |
|---|---|
| 26 | Professional component only, when the pathologist interprets but does not own the lab |
| TC | Technical component only, when the lab performs the stain but does not interpret |
| None | Global billing when the same entity performs and interprets |
Payment differs by component and setting, so check the CMS Physician Fee Schedule lookup for the professional and technical amounts in your locality.
Documentation Requirements
- Each specimen identified separately, matching the requisition.
- Every antibody listed by name, with its result.
- Medical necessity: why each stain was needed to reach or refine the diagnosis.
- Whether each stain was single, multiplex or quantitative.
- Interpretation signed by the pathologist.
Common 88342 Denials and Fixes
| Denial cause | Fix |
|---|---|
| 88341 billed without 88342 | Always report the initial stain first, per specimen |
| Units exceed the payer limit | Check MUEs; split by specimen only when documented |
| 88342 billed with 88360/88361 for the same antibody | Report the quantitative code only |
| Stains not justified in the report | Document why each antibody was ordered |
| Wrong component modifier | Match 26 or TC to who performed and interpreted |
IHC denials are expensive to lose and slow to appeal. Our pathology billing services team counts units against the report before claims go out, and denial management recovers the rest. For other lab codes, see CPT codes for laboratory billing.
Conclusion
CPT 88342 is billed once per specimen for the first antibody, 88341 for each additional antibody on that specimen, and 88344 for multiplex stains. Do not stack 88342 on a quantified marker, count antibodies rather than slides, and document why every stain was needed. Those three habits prevent most IHC denials.
Need help with pathology billing?
Dr Biller RCM codes IHC, surgical pathology and molecular services for labs and pathology groups.
CPT 88342 FAQs
Immunohistochemistry or immunocytochemistry, per specimen, for the initial single antibody stain procedure.
For each additional single antibody stain on the same specimen, as an add-on to 88342.
One per separately identified specimen. Additional antibodies on the same specimen use 88341.
88342 is a single antibody stain; 88344 is a multiplex stain that uses more than one antibody in one procedure.
Not for the same antibody on the same specimen. When a marker is quantified with 88360 or 88361, report that code instead.
No. Control slides are part of the procedure and are not billed separately.
