CPT code 88377: ISH analysis, computer-assisted, per specimen2026 Medicare rate & RVUs

Medicare pays $384.11 for 88377 nationally in the office. Local office rates run $335.94–$537.48.

Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.

What 88377 covers

This service uses computer-assisted image analysis to quantify or semiquantify in situ hybridization findings for a probe in a tissue specimen. A pathologist typically reviews the stained tissue and image-analysis results in a pathology laboratory, such as when evaluating tumor cells for a molecular marker. The analysis supplements the underlying ISH test by providing a measured assessment of the probe signal rather than a visual interpretation alone.

Report the service when the specimen undergoes the specified morphometric analysis, and identify the specimen, probe, method, and analyzed findings in the pathology record. The code is reported per specimen; the probe and analysis performed should be clear enough to support the reported service. CMS recognizes professional and technical components: modifier 26 represents interpretation, modifier TC represents equipment and staff, and reporting without either modifier represents the global service.

This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.

Where 88377 pays more and less

The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.

109 of 109 payment localities

88377 rates by state

Office rate range in each state. Select a state to see its payment localities.

How the 88377 rate is calculated

Each of 88377’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.

Payment rules and modifiers for 88377

The CMS indicators that decide how 88377 is paid alongside other services.

What modifiers do to the payment

When to use modifier 26

88377 compared with similar codes

How to choose

88367ISH analysisAutomated morphometric analysis

88377 describes quantitative or semiquantitative morphometric analysis of ISH findings per specimen. Consider 88367 when the service is computer-assisted ISH but is not the morphometric analysis described here.

88361Tumor immunohistochemistryComputer-assisted analysis

88361 is computer-assisted morphometric analysis of tumor immunohistochemistry. This code is for morphometric analysis of in situ hybridization findings.

88369ISH morphometryQuantitative or semiquantitative

Both codes concern morphometric ISH analysis. Compare the code descriptors and documented method to determine which service was performed.

Codes related to 88377

Related codes aren’t interchangeable: bill the code that matches the service performed.

Where these rates come from

FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.

CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027

Open CMS sourceHow we calculate rates