CPT 88355: Morphometric Analysis of Skeletal Muscle

CPT code 88355 represents a pathologist-performed morphometric analysis of skeletal muscle slides prepared by laboratory staff. The code captures quantitative assessment of muscle fiber size, shape, and related physical features that support diagnosis and characterization of myopathies and other neuromuscular disorders. Nationally, this analytic service informs clinical decision-making in neuromuscular medicine and pathology and is relevant to hospitals, independent pathology laboratories, and specialty clinics.

Key payers covered in the analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of clinical context for 88355, common sites of service, and payer relevance. The publication outlines typical utilization settings, expected reporting workflow (slide prep by laboratory analysts followed by qualified provider analysis), and how the code is positioned among pathology services. It also highlights available benchmarks and policy considerations where present, and notes where input data are not available. The goal is to provide clinicians, billing professionals, and policy analysts with a concise reference to understand the clinical role and billing context of CPT code 88355 at a national level.

Billing Code Overview

CPT code 88355 describes a morphometric analysis of skeletal muscle performed by a qualified provider, typically a pathologist, after laboratory slide preparation by a lab analyst. The service involves measurement and evaluation of muscle fiber size, shape, and other physical characteristics to assess muscle pathology.

Service type: Quantitative morphometric pathology analysis of skeletal muscle
Typical site of service: Hospital pathology laboratory or independent clinical pathology laboratory

Data not available in the input.

Clinical Context

A 52-year-old patient with progressive proximal muscle weakness and elevated serum creatine kinase undergoes an open muscle biopsy of the vastus lateralis. Laboratory technicians prepare histologic and immunohistochemical slides, and the pathologist performs a detailed morphometric analysis to quantify fiber size distribution, mean fiber cross-sectional area, presence of atrophy or hypertrophy, and proportions of fiber types. The analysis supports diagnosis and staging of myopathies such as inflammatory myopathy, muscular dystrophy, or toxic/drug-induced myopathy. Results are documented in the pathology report, which guides neurologists and neuromuscular specialists in clinical management and genetic testing decisions.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when reporting the pathologist's professional interpretation separate from technical slide preparation if the technical component is billed separately.
`TC`	Technical component	Use when reporting only the technical component (slide preparation) by the laboratory separate from the pathologist's interpretation.

Taxonomy Code	Specialty	Notes
2080P0200X	Anatomic Pathology	Pathologists who perform morphometric analysis and interpret biopsy slides.
2080P0220X	Clinical Pathology	Laboratory pathologists involved in diagnostic testing and reporting.
207L00000X	Neurology	Neurologists order biopsies and use results for clinical management of myopathies.
208800000X	Diagnostic Radiology	Radiologists may assist in image-guided biopsy procurement.
363A00000X	Physical Medicine & Rehabilitation	Specialists who may collaborate in function assessment and interpretation of biopsy findings.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`M60.9`	Myositis, unspecified	Muscle biopsy morphometry helps quantify fiber size and inflammatory change to support diagnosis of myositis.
`G72.0`	Drug-induced myopathy	Morphometric analysis can document patterns of muscle fiber damage from toxins or medications.
`G71.0`	Muscular dystrophy	Quantitative fiber-size distribution and connective tissue replacement aid in dystrophy evaluation and severity assessment.
`M62.50`	Muscle wasting and atrophy, unspecified site	Morphometry documents degree of atrophy and fiber-type specific involvement.
`R53.1`	Weakness	When patients present with weakness, biopsy morphometry contributes objective structural data for diagnosis.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`88355`	Morphometric analysis, skeletal muscle (pathologist-performed)	Primary code describing the pathologist's quantitative analysis of muscle fiber morphology.
`88304`	Level IV surgical pathology, gross and microscopic examination	Often billed when pathologist performs standard histologic interpretation of the biopsy in addition to morphometry.
`88342`	Immunohistochemistry, per specimen; initial single antibody stain	Frequently performed to subtype muscle disease and may be ordered alongside morphometric analysis.
`88346`	Immunohistochemistry, each additional single antibody stain	Billed for additional antibody stains required to evaluate specific proteins in muscle disease.
`88331`	Consultation (pathology) for a second opinion	Used when another pathologist provides supplemental interpretation of the morphometric findings.

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Summary & Overview