CPT Code 97113: Aquatic therapy billing and coding guide
Aquatic therapy is one of the more frequently denied outpatient therapy services...
Last Updated: September 1, 2026
Key takeaways
CPT Code 88342 covers immunohistochemistry, or IHC, for the first antibody stain on a specimen in surgical pathology
Report 88342 once per specimen per date of service, then use add-on code 88341 for each additional antibody
The 2026 Medicare national payment is $110.22 for 88342 and $94.19 for 88341, in both facility and non-facility settings
Billing 88342 more than once for the same specimen is the most common denial reason on IHC claims
Pabau’s claims management software helps pathology billing teams track IHC units, attach documentation, and submit clean claims
CPT Code 88342 is the billable code for immunohistochemistry, or IHC, covering the first single antibody stain performed on a specimen. It sits in the surgical pathology family of the CPT code set, and it is payable once per specimen per date of service.
This guide covers the official descriptor, how 88342 works alongside 88341 on one specimen, and the 2026 Medicare payment amounts. It also sets out the documentation an audit expects, the ICD-10 codes that support medical necessity, and the errors behind most IHC denials.
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CPT Code 88342: Definition and clinical description
CPT Code 88342 describes immunohistochemistry or immunocytochemistry, a tissue-based technique that uses antibody-antigen reactions to detect specific proteins in tissue or cell specimens.
The American Medical Association (AMA) maintains the CPT code set and classifies 88342 under Surgical Pathology, covering the first antibody per specimen.
Pathologists order IHC to characterize tumor type, assess prognostic markers, identify infectious organisms, or confirm lymphoma and leukemia subtypes. A single biopsy specimen may need several antibody panels.
CPT Code 88342 captures the first stain, and every subsequent antibody on that specimen is reported with add-on code 88341.
CPT Code 88342 vs 88341: First vs additional antibody
The first-versus-additional distinction is where most IHC billing errors start. Both codes describe the same technique on the same specimen. They differ only in sequence.
CPT Code 88342 is reported exactly once per specimen, however many antibodies are applied. It represents the first stain and is a standalone billable code. 88341 is an add-on code reported for each antibody beyond the first. It cannot be billed without 88342, or another qualifying parent IHC code, on the same claim.
- One specimen, one antibody: Bill 88342 only.
- One specimen, three antibodies: Bill 88342 x1 + 88341 x2.
- Two specimens (separate blocks), two antibodies each: Bill 88342 x2 + 88341 x2, with specimen identifiers in the documentation.
- Never: Bill 88342 more than once for the same antibody on the same specimen. This is a primary Medicare audit trigger.
Payer policies on unit maximums vary. Medicare imposes a one-unit-per-specimen limit on 88342. Some commercial payers apply their own caps per date of service, so check the payer’s Local Coverage Determination, or LCD, before submitting a multi-specimen claim.
Billing rules and units per specimen
Medicare limits CPT Code 88342 to one unit per specimen per date of service. The Local Coverage Determinations issued by Medicare Administrative Contractors, known as MACs, reinforce that limit. Billing more than one unit of 88342 for a single specimen on the same date is a compliance violation.
Pathology billing teams need to track three variables precisely on an IHC claim. Each one changes how many units of 88342 and 88341 are reportable:
- Specimen count: how many separately identified blocks the case covers.
- Antibody count per specimen: the first stain is 88342, and each one after it is 88341.
- Duplicate stains: whether a requested antibody repeats a stain already applied to that specimen that day.
Practice management software like Pabau validates the CPT catalog before a claim leaves the practice. A unit mismatch on 88342 then surfaces in-house instead of on a remittance advice.
Pro Tip
Flag any order requesting more than one unit of 88342 on a single specimen before submission. Build a pre-bill audit step that cross-checks specimen count against reported 88342 units. A mismatch caught in-house costs minutes. A mismatch caught by the payer costs weeks of appeals work.
2026 Medicare reimbursement for 88342 and 88341
Medicare payment for CPT Code 88342 is built from the Resource-Based Relative Value Scale, or RBRVS, and adjusted by the Geographic Practice Cost Index (GPCI). Use the CMS Physician Fee Schedule lookup tool or FastRVU’s 2026 RVU lookup to confirm the amount for your locality.
The 2026 national payment amount is $110.22 for 88342 and $94.19 for 88341. Both codes pay the same in a facility and a non-facility setting, so the place of service does not change the rate. Your locality’s GPCI still does. Applied to the unit scenarios above, those two amounts set what a whole IHC panel is worth.
The claim file sent to Medicare must carry the correct place-of-service code, 11 for office and 22 for outpatient hospital. A wrong code will not change the 88342 rate, but it can trigger a place-of-service edit and a denial. The remittance advice returned after adjudication confirms the amount paid and any line-item adjustment.
Documentation requirements that survive an audit
Documentation is the other main source of 88342 denials. CMS and most commercial payers require the medical record to establish medical necessity before the claim is approved.
The pathology report is the primary supporting document. It must carry the clinical indication, the specimen source and identifier, and each antibody applied with its clone, dilution and control tissue. It also needs the interpretation of the staining pattern and the pathologist’s conclusion.
- Clinical indication: the ordering physician’s clinical question must appear in the record, for example “rule out diffuse large B-cell lymphoma”. A generic entry like “IHC panel ordered” will not survive an audit.
- Specimen identification: each specimen block needs a unique identifier that matches the claim. Multi-specimen claims without block-level identifiers are a common audit flag.
- Antibody log: the pathology report must list every antibody applied to each specimen, with results. The antibody count drives the 88342 and 88341 units, so the log is a billing document as well as a clinical one.
- Medical necessity linkage: the ICD-10 code on the claim must be a covered indication for IHC under the applicable LCD. A mismatch between the report’s clinical question and the submitted code leads straight to a denial.
- Pathologist attestation: the interpreting pathologist must sign the report. Unsigned or incomplete reports will not satisfy an audit.
Retention matters as much as content. For a laboratory accredited by the College of American Pathologists (CAP), the Anatomic Pathology Checklist sets the standard. It requires a 10-year minimum for surgical pathology reports, slides and blocks. Some MAC jurisdictions and state laws run longer, so hold to whichever period is longest.
Covered ICD-10 diagnosis codes
Medicare covers immunohistochemistry when it is medically necessary for a diagnosis or a treatment decision. Medical necessity comes from the clinical context in the record rather than from the panel itself.
The codes below are categories that Medicare LCDs and major commercial policies commonly accept. Covered indications differ by contractor, so check the LCD active in your region before you submit.
Codes for neoplasms of uncertain behavior (D37-D48) matter most for IHC billing, because they describe the diagnostic uncertainty IHC is meant to resolve. Using a definitive malignancy code before the pathologist has confirmed malignancy is a compliance risk. The full ICD-10-CM code library carries the descriptors and coding notes for each family above.
How 88342 interacts with related CPT codes
Pathology billing rarely involves a single code. An IHC case usually carries several codes from the surgical pathology family, and knowing how they interact prevents both unbundling and over-reporting. The AAPC’s CPT code reference gives searchable detail on each one.
One nuance catches billing teams out. CMS National Correct Coding Initiative (NCCI) procedure-to-procedure edits bundle 88342 and 88341 with 88360 and 88361. Reporting a quantitative Ki-67 analysis alongside standard IHC staining on the same specimen therefore needs modifier 59 or XU.
The record has to document a distinct antibody or a distinct method for the second service. Without that, the NCCI edit will deny the bundled line.
IHC rarely appears on a claim by itself. The specimen it runs on carries its own surgical pathology examination code, often 88305, so the two travel together on the same claim.
Common billing errors and denial reasons
IHC claims generate a disproportionate share of pathology denials, because of the unit rules and the specificity payers expect in the record. Five error patterns account for most of them, and each one is catchable before the claim leaves the practice.
- Billing 88342 more than once for one specimen: Medicare allows exactly one unit per specimen. Additional stains on that specimen use 88341. Submitting 88342 x3 for a single specimen triggers an automatic edit in most MAC systems and a full denial.
- Billing 88341 without its parent code: add-on code 88341 needs a qualifying parent code on the same claim, which is 88342, 88344 or 88360. Claims carrying only 88341 are rejected before adjudication begins.
- Using 88342 for a multiplex assay: when one assay run detects two or more antigens, 88344 is the correct code. Reporting 88342 for a multiplex procedure misstates the service performed.
- An ICD-10 code the LCD does not cover: submitting 88342 with a diagnosis the MAC’s LCD does not list produces a medical necessity denial. The diagnosis must match the clinical question in the pathology report.
- An unsigned or incomplete pathology report: payers request records during post-payment audits. A claim with no complete signed report, specimen identification, antibody log and interpretation is exposed to recoupment.
Patterns matter more than individual denials. A single denial may be a one-off. Repeated CO-4 or CO-11 denials on IHC claims point to a process problem that needs a root-cause fix. CO-4 flags an inconsistent modifier and CO-11 a diagnosis inconsistent with the procedure.
Pro Tip
Run a quarterly audit on all 88342 claims submitted in the previous 90 days. Filter for any claim where 88342 appears more than once per date of service per patient. Cross-reference against the pathology report to confirm whether multiple specimens were documented. This single step catches the most expensive recurring error in IHC billing.
How practice management software supports IHC billing accuracy
A pathology lab billing CPT Code 88342 has a tracking problem most general-purpose billing systems were not built for. It has to tie multi-specimen orders to individual claim lines, count antibodies per specimen, and hold an audit trail a MAC will accept. That is the work audit-ready claims management software is designed to absorb.
Pabau connects to a US clearinghouse for claim submission, real-time eligibility checks and remittance reconciliation in one workflow. Built-in CPT and ICD-10 catalogs flag a coding error at the point of entry. A unit mismatch on 88342 is caught before submission, not during a post-payment audit.
The payoff for a pathology billing team is fewer rework cycles. Denials that used to take weeks of appeals work get resolved in the minutes before a claim goes out.
Reduce IHC claim denials with Pabau
Pabau’s claims management tools help pathology billing teams track specimen units, validate CPT codes, and submit clean claims through integrated clearinghouse workflows. See how it works for your practice.
Conclusion
The unit rule is the whole game with 88342. Get the specimen count and the antibody count right, and the code almost bills itself. Get them wrong and no amount of appeal work recovers the margin the rework consumed.
So the fix belongs upstream, in the pre-bill check rather than the appeals queue. A pathology lab that cross-checks specimen count against reported 88342 units every time will see its IHC denial rate fall without hiring anyone. Book a demo to see how Pabau catches unit and eligibility errors before an IHC claim reaches the payer.
Continue your research
Need to understand how clearinghouse submissions work? Claim.MD clearinghouse overview explains how electronic claims flow from practice to payer and where errors are caught.
Seeing repeated denial patterns across pathology claims? Denial codes in medical billing covers the most common CO and PR adjustment reason codes and what they mean for your revenue cycle.
Want to verify eligibility before IHC orders are processed? Insurance eligibility verification walks through how real-time eligibility checks reduce surprise denials on pathology claims.
Building a pre-bill audit step for your lab? Medical billing compliance sets out the record-keeping and review controls that hold up under a post-payment audit.
Need to know what the payer actually receives? The 837 claim file breaks down the electronic claim format, field by field, including where units and place of service sit.
Frequently asked questions
What does CPT Code 88342 describe?
CPT Code 88342 is immunohistochemistry (IHC) or immunocytochemistry performed per specimen for the initial single antibody stain procedure. It falls under the surgical pathology family in the AMA’s CPT code set. Pathologists use it to detect specific proteins or antigens in tissue through antibody-antigen reactions, most commonly for tumor typing.
What is the difference between CPT 88342 and CPT 88341?
CPT 88342 covers the first antibody stain applied to a specimen and is reported once per specimen per date of service. CPT 88341 is an add-on code reported for each additional antibody applied to the same specimen beyond the first. So a panel of four antibodies on one specimen would be billed as 88342 x1 plus 88341 x3. 88341 cannot be billed without a qualifying parent code like 88342 on the same claim.
How many units of CPT 88342 can be billed per specimen?
Medicare limits CPT Code 88342 to one unit per specimen per date of service. Billing 88342 more than once for the same specimen on the same date is a compliance violation and a primary audit trigger. When multiple specimens are submitted on the same date, each one supports its own unit of 88342. The pathology documentation has to identify each specimen separately.
What is the Medicare reimbursement rate for CPT 88342 in 2026?
The 2026 Medicare national payment amount for CPT 88342 is $110.22 per specimen. The add-on code 88341 pays $94.19. Both amounts are the same in facility and non-facility settings, so place of service does not change the rate. Your locality’s GPCI adjustment does, so confirm the figure with the CMS Physician Fee Schedule lookup tool.
Can CPT 88342 and 88341 be billed on the same date of service?
Yes. CPT 88342 and 88341 are routinely billed together when a single specimen receives multiple antibody stains. 88342 covers the first antibody, and 88341 covers each additional one. They must appear on the same claim, and the pathology report must document each antibody applied and the clinical basis for the panel.
What are common billing errors associated with CPT Code 88342?
The most frequent error is billing 88342 more than once per specimen. Two others are submitting 88341 without its parent 88342, and using 88342 for a multiplex assay when 88344 is correct. Two more are linking the claim to an ICD-10 code the applicable MAC LCD does not cover, and filing without a complete signed pathology report. Each error has a distinct fix and a distinct denial code pattern.
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