Summary & Overview
CPT 88377: Single-Multiplex In Situ Hybridization Probe Stain and Evaluation
CPT code 88377 represents single-multiplex in situ hybridization (ISH) testing with manual evaluation by a qualified provider, commonly performed on tumor tissue. This pathology procedure supports diagnostic and prognostic decision-making by detecting and localizing nucleic acid targets within tissue sections. Nationally, the code matters because ISH-based assays inform targeted therapy selection and biomarker-driven care pathways across oncology and other specialties.
Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise outline of what the code covers, typical clinical contexts and sites of service, and the common payment and coverage considerations associated with laboratory pathology codes. The publication provides benchmarks and policy context relevant to billing and claim adjudication, highlights clinical applications in tumor testing, and notes where data are not available in the input. The goal is to give clinical, coding, and revenue teams a clear, national-level primer on CPT code 88377 to support accurate documentation, coding, and payer discussions.
Billing Code Overview
CPT code 88377 describes a pathology service in which a lab analyst applies a single multiplex in situ hybridization (ISH) probe stain to slide(s) prepared from a single patient specimen, such as tumor tissue. A qualified provider, typically a pathologist, then evaluates the stained slide(s), including manual counting or estimation of the number and location of probes.
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Service type: Laboratory pathology diagnostic testing involving single-multiplex ISH probe staining and interpretive evaluation by a qualified provider.
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Typical site of service: Hospital or independent pathology laboratory, clinical pathology department, or other specialized diagnostic laboratory where tissue specimens and slide-based ISH testing are performed.
Data not available in the input for associated taxonomies, ICD-10 diagnoses, and related codes.
Clinical & Coding Specifications
Clinical Context
A middle-aged patient with a newly identified breast mass undergoes image-guided core needle biopsy. The tissue specimen is submitted to the pathology laboratory where a lab analyst performs a single multiplex in situ hybridization (ISH) probe stain on slides prepared from the biopsy. A pathologist then evaluates the stained slides, manually counting or estimating probe signals to assess gene copy number or rearrangement (for example HER2 amplification or ALK rearrangement) to guide targeted therapy selection. Typical workflow: biopsy → formalin fixation and processing → slide preparation → multiplex ISH staining (88377 performed by lab technical staff) → pathologist review and manual counting/interpretation (professional component) → pathology report issued to the ordering oncologist/surgeon. Typical site of service is a hospital outpatient pathology lab, independent clinical laboratory, or hospital inpatient laboratory supporting oncology, surgical pathology, or molecular diagnostics.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when billing only the pathologist's interpretation/report for the ISH stain separate from technical staining. |
TC |