Summary & Overview
CPT 88365: In Situ Hybridization Single Probe Stain with Interpretation
CPT code 88365 designates an initial in situ hybridization (ISH) single probe stain applied to slide(s) from a single patient specimen, followed by a qualified provider’s qualitative interpretation to support a pathologic diagnosis. This molecular pathology service is commonly used for tumor tissue evaluation and can influence diagnostic subtyping, prognostic assessment, and treatment selection. Nationally, use of targeted molecular and cytogenetic assays has grown, making accurate coding for ISH procedures important for clinical documentation and claims processing.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of the clinical role of 88365, payer coverage considerations, common modifiers encountered on claims, and benchmark points where available. The publication summarizes typical sites of service and the clinical context in which the service is ordered, and it outlines documentation elements relevant to claim adjudication.
This resource is intended for billing managers, laboratory directors, and pathology providers seeking concise guidance on what CPT code 88365 represents, where it is applied clinically, and what payers generally consider when processing claims for initial ISH single probe staining with qualitative interpretation.
Billing Code Overview
CPT code 88365 describes an in situ hybridization (ISH) single probe stain where a laboratory analyst applies an initial ISH single probe stain to slide(s) prepared from a single patient specimen, commonly tumor tissue. A qualified provider, typically a pathologist, then performs a qualitative interpretation of the stained slide(s) to arrive at a pathologic diagnosis.
Service type: Anatomic pathology — molecular diagnostic staining and interpretation
Typical site of service: Clinical laboratory or hospital pathology department, with slides prepared from biopsy or surgical tumor specimens
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Clinical & Coding Specifications
Clinical Context
A 62-year-old patient presents with a biopsy-confirmed mass in the lung. A tissue specimen is submitted to the pathology laboratory for molecular and morphologic workup. The laboratory technician performs an initial in situ hybridization single probe stain on slides prepared from the tumor specimen to detect a specific gene amplification or translocation. A pathologist then qualitatively reviews the stained slides using light microscopy, documents the presence or absence of the target signal pattern, and issues a pathology report that integrates the ISH result with histology and other ancillary testing to establish tumor classification and guide targeted therapy selection. Typical workflow steps include specimen accessioning, slide preparation and staining by the histology/ISH technologist, pathologist interpretation and documentation, and transmission of the result to the treating oncology team. Typical site of service is an anatomic pathology laboratory within a hospital or independent reference lab; the service is ordered by the treating oncologist or surgeon and is performed on tissue from an outpatient clinic or inpatient procedure.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when reporting only the pathologist’s interpretation component, separate from the laboratory technical work. |