Summary & Overview

HCPCS G0462: Additional Immunohistochemistry/Immunocytochemistry Stain

HCPCS Level II code G0462 denotes an add-on pathology service for immunohistochemistry or immunocytochemistry: each additional single or multiplex antibody stain performed per specimen. This code matters nationally because immunostains are essential for diagnostic precision in oncology, infectious disease, and other tissue-based diagnoses, and add-on coding affects laboratory billing, clinical documentation, and payer coverage decisions. Key payers in this overview include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare.

Readers will find practical benchmarks for utilization of add-on immunostain coding, a concise clinical context explaining when additional antibody stains are indicated, and an outline of common payer coverage considerations and billing practices. The publication summarizes typical sites of service where G0462 is reported and highlights common modifiers and coding conventions relevant to pathology labs and surgical pathology services. Data not available in the input is noted where applicable. The intent is to provide a national perspective on the role of G0462 in laboratory billing and clinical workflows, and to clarify the scope and use of this HCPCS Level II add-on code.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareG0462HCPCS Level IIimmunohistochemistryimmunocytochemistrypathologylaboratory-billingadd-on-codesurgical-pathologydiagnostic-staining

Billing Code Overview

HCPCS Level II code G0462 describes immunohistochemistry or immunocytochemistry, per specimen; each additional single or multiplex antibody stain. The code represents an add-on laboratory pathology service used when additional antibody stains are performed on a tissue or cytology specimen beyond the primary procedure.

Service Type: Pathology / Laboratory — immunohistochemistry/immunocytochemistry add-on service

Typical Site of Service: Hospital pathology laboratory, independent pathology laboratory, reference laboratory, or outpatient surgical pathology service

Clinical & Coding Specifications

Clinical Context

A surgical pathology laboratory receives a skin biopsy from a 62-year-old patient with a pigmented lesion suspicious for melanoma. The specimen is accessioned and the pathologist performs routine H&E staining. To further characterize tumor subtype and confirm diagnosis, the pathologist orders immunohistochemistry stains. The primary IHC panel includes markers such as S100, SOX10, HMB-45, and Melan-A. When additional single or multiplex antibody stains beyond the primary panel are required to clarify tumor differentiation or to evaluate metastatic markers (for example cytokeratin subtypes, EMA, or CD45), the laboratory bills each additional antibody stain using code G0462 in addition to the primary procedure code.

Clinical workflow:

The clinician performs the biopsy in an outpatient dermatology clinic and submits the specimen to the pathology lab.
The pathology accession team logs the specimen and assigns identifiers.
The histotechnologist prepares slides and performs H&E staining; the pathologist reviews initial morphology.
The pathologist selects a primary IHC panel and, if necessary, orders additional single or multiplex antibody stains.
The laboratory performs the additional antibody stain(s) and documents technical and, if applicable, professional components for billing using modifier 26 for the professional component and TC for the technical component as appropriate.
The pathologist issues a final report integrating morphology and immunohistochemistry results for clinical management.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	When billing only the pathologists interpretation/reporting portion of the IHC test.
`TC`	Technical component	When billing only the laboratory/technical component (staining, slide prep, instrumentation) of the IHC test.
`59`	Distinct procedural service	When another billed service is distinct and separate from the IHC stain on a different specimen or encounter (use cautiously with documentation).
`76`	Repeat procedure by same provider	When an additional identical IHC stain is repeated by the same laboratory on the same day for a new reason.
`77`	Repeat procedure by another provider	When an identical additional IHC stain is performed by a different provider/lab on the same day.
`90`	Reference (outside) laboratory	When the IHC stain is performed by an outside/reference laboratory and billed by the performing lab.
`XU`	Unusual non-overlapping service (Modifier X, part of NCCI)	When an additional service is separately identifiable and distinct from other services on the same day (use per payor guidelines).
`Q0`	Services furnished under an FDA investigational device exemption, clinical study	When IHC staining is part of a clinical trial under IDE/IDE-equivalent when allowed.
`QW`	CLIA waived test	Rare for IHC; used when a waived test is billed separately (seldom applicable to IHC).
`GP`	Professional services furnished by a physical therapist	Not typically applicable; included here for completeness in certain multidisciplinary billing workflows.

Taxonomy Code	Specialty	Notes
`207RH0000X`	Anatomic Pathology	Primary specialty performing IHC interpretation and reporting.
`207RK0000X`	Clinical Pathology	Laboratories performing technical staining and laboratory oversight.
`208000000X`	Dermatology	Clinician submitting skin biopsy specimens for IHC evaluation.
`207L00000X`	Hematopathology	Specialist who orders and interprets IHC panels for lymphoid neoplasms.
`207T00000X`	Surgical Pathology	Pathologists who integrate morphology with IHC for surgical specimens.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`C43.9`	Malignant melanoma of skin, unspecified	IHC panels help confirm melanocytic differentiation and rule out mimics when morphology is equivocal.
`D22.9`	Melanocytic nevi, unspecified	IHC may be used in challenging nevi to differentiate benign from malignant melanocytic proliferations.
`C50.9`	Malignant neoplasm of breast, unspecified	Additional IHC stains (e.g., cytokeratins, ER/PR, HER2 testing adjuncts) may be performed to subtype tumors.
`C77.9`	Secondary and unspecified malignant neoplasm of lymph nodes	IHC assists in identifying primary site and cell lineage in nodal metastases.
`C80.1`	Malignant (primary) neoplasm, unspecified site	When site is uncertain, broad IHC panels including additional stains billed with `G0462` can help determine origin.
`D37.9`	Neoplasm of uncertain behavior of skin, unspecified	IHC may clarify tumor behavior when morphological assessment is indeterminate.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`88342`	Immunohistochemistry or immunocytochemistry, per specimen; initial single antibody stain	Often billed as the primary IHC procedure; `G0462` is used for each additional antibody stain beyond the primary billed `88342`.
`88341`	Immunohistochemistry or immunocytochemistry, per specimen; first stain of a multi-stain panel (sometimes used interchangeably with `88342` depending on payer)	May represent the primary stain in a multi-stain panel; additional stains billed with `G0462`.
`88348`	Morphometric analysis, immunohistochemistry	Performed when quantification of staining (e.g., H-score) is required after antibody stains like those billed with `G0462`.
`88360`	Microscopic examination, surgical pathology, gross and microscopic, with frozen sections when performed	Often precedes IHC for intraoperative consultation; final IHC (additional stains billed with `G0462`) occurs after permanent sections.
`88305`	Level IV surgical pathology, gross and microscopic examination	Routine diagnostic surgical pathology that commonly triggers reflex IHC testing; additional stains are billed with `G0462` when needed.