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.