Summary & Overview
CPT 81504: RNA Expression Tumor Origin Classifier
CPT code 81504 represents an RNA expression–based molecular diagnostic assay that matches a tumor’s transcriptional profile to a reference database to infer likely tissue of origin for cancers of unknown primary. The test is used nationally to help guide diagnostic workups and therapy selection when the primary tumor site is uncertain. Its clinical value lies in narrowing diagnostic possibilities and informing downstream management.
Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical purpose and typical sites of service, payer coverage context, and implications for laboratory service lines. The publication highlights common billing and coding considerations for laboratories and health plans, and summarizes available policy elements and benchmarking topics relevant to molecular diagnostic oncology testing.
This summary provides practical context for clinicians, laboratory managers, and payers evaluating the role of an RNA expression–based tumor origin classifier in diagnostic pathways, without state-specific policy details. Data not available in the input are explicitly noted where applicable in supporting sections.
Billing Code Overview
CPT code 81504 describes a molecular diagnostic test that compares the RNA expression profile of a tumor of unknown primary origin to a reference tumor database to identify the most likely tissue or site of origin. This service type is a molecular diagnostic tumor origin classifier that analyzes tumor RNA expression patterns.
Typical site of service: clinical laboratory or specialized molecular diagnostics laboratory. The test is performed on tumor tissue specimens and reported by laboratories that provide advanced genomic and transcriptomic profiling.
Clinical & Coding Specifications
Clinical Context
A 62-year-old patient presents with a metastatic tumor identified on imaging but without a definitive primary site after standard pathology and immunohistochemistry. The oncology team orders an RNA expression profiling assay to compare the tumor's gene expression signature against a reference tumor database to suggest the most likely tissue or tumor type of origin. A formalin-fixed paraffin-embedded (FFPE) tumor specimen or extracted RNA is sent from the pathology laboratory to a reference molecular diagnostics laboratory. The laboratory performs extraction, quality control, RNA sequencing or targeted expression profiling, bioinformatic analysis to generate a similarity score, and a report that includes the top probable tumor types and confidence metrics. The result informs tumor-directed systemic therapy selection, targeted therapy considerations, and decisions about additional diagnostic workup. Typical sites of service include outpatient pathology laboratories, independent molecular diagnostic reference labs, hospital-based molecular labs, and cancer center specimen collection areas. Billing occurs under the molecular pathology/proprietary algorithm code 81504 for the tumor origin RNA expression comparison service.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when billing only the professional interpretation component separate from the technical processing if the lab splits TC/26 billing. |