What Does ICD-10 Code C81.90 Mean?
ICD-10 code C81.90 designates Hodgkin lymphoma when neither the histologic subtype nor the anatomic site of involvement can be determined from available clinical documentation. This code represents a valid, billable diagnosis under the ICD-10-CM classification system for malignant neoplasms of lymphoid, hematopoietic, and related tissue. C81.90 functions as the default selection within the C81 category when a provider confirms Hodgkin lymphoma through pathology but the medical record lacks sufficient detail to assign a more specific code.
Key attributes of C81.90:
- Valid for all HIPAA-covered transactions from October 1, 2025 through September 30, 2026
- Billable as a principal or secondary diagnosis in both inpatient and outpatient settings
- Requires confirmation of Hodgkin lymphoma diagnosis, typically via biopsy with Reed-Sternberg cell identification
- Appropriate only when documentation truly lacks subtype or site specificity
- Not a substitute for incomplete record review or inadequate physician queries
What Conditions and Diagnoses Does C81.90 Cover?
C81.90 applies when clinical documentation confirms Hodgkin lymphoma but fails to specify which of the recognized subtypes is present or where the disease is anatomically located. This scenario commonly arises during initial diagnostic workups, when pathology reports state “Hodgkin lymphoma” without further classification, or when legacy records use outdated terminology like “Hodgkin disease” without subtype detail.
Clinical scenarios appropriate for C81.90:
- Pathology report states “Hodgkin lymphoma” without identifying classical versus nodular lymphocyte-predominant type
- Biopsy confirms Reed-Sternberg cells but does not specify nodular sclerosis, mixed cellularity, lymphocyte-rich, or lymphocyte-depleted subtype
- Documentation describes “Hodgkin disease” using older nomenclature without current ICD-10-CM subtype details
- Provider documents Hodgkin lymphoma diagnosis but medical record contains no anatomic site designation for lymph node involvement
- External records transferred from another facility confirm Hodgkin lymphoma but omit classification details necessary for specific code assignment
What Does This Code Specifically Exclude?
C81.90 should never be assigned when documentation supports a more specific diagnosis code. The following conditions require different code selections:
- Personal history of Hodgkin lymphoma in a patient now disease-free: Use Z85.71, not C81.90
- Hodgkin lymphoma explicitly documented as in remission: Use C81.9A, not C81.90
- Any Hodgkin lymphoma subtype identified in pathology: Use specific codes C81.00-C81.49 based on subtype
- Hodgkin lymphoma with documented anatomic site: Use specific fifth-character extensions C81.91-C81.99 based on location
- Non-Hodgkin lymphoma: Use C85.90 or other appropriate C82-C85 codes
- Active treatment follow-up when remission status is documented: Query provider for remission code C81.9A versus active disease code
When Is C81.90 the Right Code to Use?
Selecting C81.90 requires careful evaluation of the medical record to confirm both that Hodgkin lymphoma exists and that insufficient detail prevents more specific coding. In practice, coders frequently encounter this code during initial oncology consultations or when reviewing outside hospital records that predate current staging workups.
Step-by-step criteria for correct code selection:
- Verify pathology confirmation: Confirm the medical record contains biopsy or cytology results explicitly stating Hodgkin lymphoma or documenting Reed-Sternberg cells in appropriate clinical context.
- Search for subtype documentation: Review pathology reports, oncology notes, and diagnostic imaging reports for any mention of nodular sclerosis, mixed cellularity, lymphocyte-rich, lymphocyte-depleted, or nodular lymphocyte-predominant subtypes.
- Identify anatomic site references: Check all clinical notes, radiology reports, and procedure documentation for references to specific lymph node regions such as cervical, axillary, mediastinal, or other anatomic locations.
- Assess remission status: Determine whether the encounter addresses active disease or follow-up care for a patient in remission, as this distinction changes code selection entirely.
- Query when appropriate: If documentation appears incomplete but the chart suggests more specific information may be available, submit a compliant physician query before defaulting to C81.90.
- Apply unspecified code only when justified: Assign C81.90 exclusively when steps 1-5 confirm Hodgkin lymphoma exists but clinical information genuinely does not support a more specific code.
How Does C81.90 Differ From More Specific Hodgkin Lymphoma Codes?
Understanding when to use C81.90 versus more specific alternatives prevents under-coding and ensures optimal claim specificity. The table below clarifies the most commonly confused code relationships:
| ICD-10 Code | Code Description | Key Distinguishing Feature | When to Use Instead of C81.90 |
|---|---|---|---|
| C81.10 | Nodular sclerosis Hodgkin lymphoma, unspecified site | Pathology identifies nodular sclerosis subtype | Documentation explicitly states “nodular sclerosis” or “NS Hodgkin” even without site |
| C81.20 | Mixed cellularity Hodgkin lymphoma, unspecified site | Pathology identifies mixed cellularity subtype | Report describes “mixed cellularity” or “MC type” Hodgkin lymphoma |
| C81.40 | Lymphocyte-rich Hodgkin lymphoma, unspecified site | Pathology identifies lymphocyte-rich classic subtype | Documentation specifies “lymphocyte-rich classical Hodgkin lymphoma” |
| C81.00 | Nodular lymphocyte predominant Hodgkin lymphoma, unspecified site | Pathology identifies nodular lymphocyte-predominant type | Report states “NLPHL” or “nodular lymphocyte-predominant” variant |
| C81.91 | Hodgkin lymphoma, unspecified, lymph nodes of head, face, and neck | Site is specified as cervical, facial, or neck region | Any documentation identifies lymph nodes in head/neck area |
| C81.9A | Hodgkin lymphoma, unspecified, in remission | Patient documented as in remission | Provider explicitly states “in remission” or surveillance visit for disease-free patient |
| Z85.71 | Personal history of Hodgkin lymphoma | Patient previously treated, now cancer-free | Follow-up visit years after treatment with no active disease |
What Documentation Is Required to Support C81.90?
Medical record documentation supporting C81.90 must demonstrate both the presence of Hodgkin lymphoma and the genuine absence of information needed for more specific coding. Auditors reviewing C81.90 claims examine pathology reports first, then cross-reference clinical notes to verify whether additional specificity exists elsewhere in the chart.
What Must the Provider Document in the Clinical Notes?
The following documentation elements establish medical necessity and code validity for C81.90:
- Confirmed Hodgkin lymphoma diagnosis: Explicit statement that patient has Hodgkin lymphoma, supported by pathology results within the medical record
- Pathology report presence: Biopsy or excisional lymph node pathology report confirming Reed-Sternberg cells or explicit diagnosis of Hodgkin lymphoma
- Absence of subtype classification: Documentation showing pathology did not classify disease as nodular sclerosis, mixed cellularity, lymphocyte-rich, lymphocyte-depleted, or nodular lymphocyte-predominant
- Treatment planning or diagnostic workup notes: Clinical notes discussing Hodgkin lymphoma management, staging workup, or treatment planning that reference the diagnosis
- Rationale for unspecified status if applicable: In some cases, notes may explain why further classification is pending additional testing or why historical records lack detail
- Date of diagnosis or initial presentation: Clear documentation establishing when Hodgkin lymphoma was first identified, particularly important for distinguishing active disease from surveillance visits
Which Diagnostic or Lab Results Support This Code?
C81.90 requires objective diagnostic confirmation rather than clinical suspicion alone. The following test results provide necessary support:
- Lymph node biopsy pathology report: Core documentation source; must state “Hodgkin lymphoma” or describe Reed-Sternberg cells in appropriate pathologic context
- Excisional lymph node pathology: Provides definitive tissue diagnosis; report must confirm Hodgkin lymphoma even if subtype unspecified
- Immunohistochemistry results: CD15 and CD30 positive staining patterns consistent with classical Hodgkin lymphoma support the diagnosis when pathology report lacks subtype detail
- Flow cytometry findings: May support Hodgkin lymphoma diagnosis in some cases, though typically less definitive than tissue pathology
- Bone marrow biopsy results (if applicable): When Hodgkin lymphoma involves bone marrow and documentation does not specify subtype or other sites
- PET/CT or diagnostic imaging reports: While imaging does not confirm the code directly, reports describing lymphadenopathy or mass lesions consistent with lymphoma support medical necessity for the diagnosis
What Is the Documentation Standard for Inpatient vs. Outpatient Settings?
Documentation requirements differ slightly based on encounter setting, particularly regarding query practices and specificity expectations:
| Documentation Element | Inpatient Standard | Outpatient Standard |
|---|---|---|
| Pathology confirmation | Must be present in medical record or clearly referenced from outside facility | Must be present or explicitly referenced; coders cannot assume diagnosis without documentation |
| Query threshold | Query required if chart suggests more specific information may be available from treating physician | Query appropriate for incomplete documentation; unspecified code acceptable if outside records lack detail |
| Treatment documentation | Chemotherapy, radiation, or procedural treatment notes must link to Hodgkin lymphoma diagnosis | Treatment plans or oncology visit notes should reference the lymphoma diagnosis |
| Site specificity | Higher specificity expected for surgical procedures or radiation therapy planning | Site often unspecified during initial diagnostic or medical oncology visits |
| Remission status | Critical to document for DRG assignment and severity adjustment | Important for longitudinal tracking but may be less immediately critical for single encounter |
How Does C81.90 Affect Medical Billing and Claims?
C81.90 carries significant financial implications due to its classification as a malignant neoplasm and its impact on diagnostic related group assignments in the inpatient setting. Understanding payer expectations and common billing patterns prevents claim denials and ensures appropriate reimbursement.
Key billing considerations:
- DRG assignment impact: C81.90 groups into MS-DRGs 820-825 or 840-842 depending on procedures performed and complications present, with relative weights ranging from moderate to high severity
- Medical necessity threshold: Payers expect high-cost treatments like chemotherapy or immunotherapy to be supported by confirmed cancer diagnosis, making pathology documentation critical
- Specificity pressure from payers: Some Medicare Administrative Contractors and commercial payers audit unspecified codes more frequently than specific alternatives, requiring solid documentation defense
- HCC risk adjustment: Hodgkin lymphoma affects Hierarchical Condition Category coding in Medicare Advantage plans, making accurate diagnosis coding essential for proper risk score calculation
- Secondary diagnosis considerations: C81.90 often appears as secondary diagnosis when patient presents with complications like infection during chemotherapy or admits for treatment-related issues
What CPT or Procedure Codes Are Commonly Billed With C81.90?
Hodgkin lymphoma treatment involves a predictable range of procedures and services that pair with C81.90 on claims. The table below outlines typical CPT code combinations:
| CPT Code | Procedure Description | Typical Pairing Context |
|---|---|---|
| 38500 | Lymph node biopsy, open | Initial diagnostic encounter when confirming Hodgkin lymphoma |
| 38792 | Injection procedure for sentinel lymph node identification | Surgical staging procedures in conjunction with lymphoma workup |
| 88305 | Tissue examination by pathologist, lymph node | Professional component for pathology interpretation establishing diagnosis |
| 96413 | Chemotherapy administration, IV infusion, first hour | Standard outpatient chemotherapy delivery for Hodgkin lymphoma treatment |
| 96415 | Chemotherapy administration, IV infusion, each additional hour | Continuation billing for extended chemotherapy infusion sessions |
| 77014 | CT guidance for placement of radiation therapy fields | Radiation oncology planning for Hodgkin lymphoma treatment |
| 99215 | Office visit, established patient, high complexity | Oncology follow-up visits with treatment planning or management |
| 99285 | Emergency department visit, high severity | ED presentation with lymphoma-related complications |
Are There Any Prior Authorization or Coverage Restrictions?
Payer policies vary significantly for Hodgkin lymphoma treatment services, making verification essential before scheduling high-cost procedures:
- Chemotherapy pre-authorization: Most commercial payers and Medicare Advantage plans require prior authorization for multi-agent chemotherapy regimens like ABVD or escalated BEACOPP protocols
- PET scan limitations: Medicare Local Coverage Determinations often restrict PET/CT frequency to specific staging and restaging timeframes; baseline, mid-treatment, and post-treatment scans typically covered
- Stem cell transplant requirements: Autologous stem cell transplant requires extensive prior authorization with documented medical necessity criteria, usually for relapsed or refractory disease
- Immunotherapy restrictions: Newer checkpoint inhibitors and targeted therapies may face coverage limitations or require step therapy documentation showing conventional treatment failure
- Site of service considerations: Some payers mandate outpatient hospital or office-based infusion rather than hospital inpatient administration for standard chemotherapy protocols
- Clinical trial exclusions: Patients enrolled in clinical trials may face coverage limitations for certain services deemed investigational
What Coding Errors Should You Avoid With C81.90?
Common mistakes with C81.90 typically stem from incomplete documentation review, failure to query providers when appropriate, or misunderstanding when unspecified codes are acceptable versus when they indicate inadequate coding practices.
Top coding errors ranked by audit frequency:
- Using C81.90 when pathology specifies subtype: Assigning the unspecified code despite pathology report clearly stating “nodular sclerosis Hodgkin lymphoma” or other specific variant represents under-coding and fails to capture maximum claim specificity.
- Failing to query when chart suggests additional information: When oncology notes discuss “nodular sclerosis type” or reference specific subtypes but pathology report does not match, coders must query rather than default to unspecified code.
- Confusing remission status with unspecified type: Assigning C81.90 for surveillance visits when patient is documented as “in remission” creates incorrect disease status reporting; C81.9A is required instead.
- Missing site-specific documentation: Overlooking radiology reports or procedure notes that clearly identify lymph node location results in using C81.90 when fifth-character site extensions (C81.91-C81.99) are supported by documentation.
- Applying C81.90 to personal history cases: Using an active disease code for patients who completed treatment years ago and have no evidence of disease represents a fundamental coding error; Z85.71 is correct for true history scenarios.
- Ignoring ICD-10-CM Official Guidelines: The guidelines explicitly state unspecified codes are acceptable only when information is truly unknown, not as a substitute for thorough chart review or appropriate queries.
What Do Auditors Look for When Reviewing Claims With C81.90?
Understanding audit focus areas helps coders ensure documentation supports code assignment before claim submission:
- Pathology report verification: Auditors immediately request pathology reports when C81.90 appears; absence of tissue diagnosis or reliance solely on clinical impression triggers denials
- Chart-to-code alignment: Line-by-line documentation review comparing clinical notes against code selection to identify any missed specificity opportunities
- Query compliance assessment: Evaluation of whether appropriate physician queries were submitted when documentation appeared incomplete or contradictory
- Pattern analysis across patient encounters: Auditors flag providers or coders who consistently use unspecified codes at rates exceeding peer benchmarks
- DRG impact review: Inpatient claims undergo additional scrutiny when C81.90 affects DRG assignment or severity classification
- Remission status verification: Follow-up visit claims are audited to ensure proper distinction between active disease codes and personal history codes
How Does C81.90 Relate to Other ICD-10 Codes?
Understanding code relationships within the broader ICD-10-CM classification system helps coders navigate complex clinical scenarios and select optimal code combinations.
| Related ICD-10 Code | Relationship Type | Key Clinical Distinction |
|---|---|---|
| C81.10-C81.19 | More specific alternative | Use when nodular sclerosis subtype is documented with or without site specification |
| C81.20-C81.29 | More specific alternative | Use when mixed cellularity subtype is documented with or without site specification |
| C81.00-C81.09 | More specific alternative | Use when nodular lymphocyte-predominant variant is documented |
| C81.9A | Remission status alternative | Use when documentation explicitly states patient is in remission |
| Z85.71 | History code alternative | Use for patients with no active disease following completed treatment |
| C85.90 | Exclusion — different disease | Never code together; use for Non-Hodgkin lymphoma when Hodgkin lymphoma is ruled out |
| D49.81 | Rule-out diagnosis alternative | Use for neoplasm of uncertain behavior when final pathology is pending |
| R59.1 | Symptom code | May be coded alongside C81.90 when generalized lymphadenopathy is a presenting symptom |
| C77.x | Secondary malignancy code | Use additional code if lymphoma metastasizes to specific lymph node regions beyond primary site |
What Is the Correct Code Sequencing When C81.90 Appears With Other Diagnoses?
Proper sequencing follows ICD-10-CM Official Guidelines for Coding and Reporting, particularly Section II for selection of principal diagnosis and Section IV for outpatient coding:
- Principal diagnosis for inpatient admission: C81.90 should be sequenced as principal diagnosis when patient is admitted specifically for Hodgkin lymphoma treatment, staging workup, or management of the malignancy itself.
- Complication as principal diagnosis: When admission addresses a complication like neutropenic fever or sepsis during chemotherapy, the complication code sequences first with C81.90 as secondary diagnosis.
- Symptom-driven encounter sequencing: For outpatient encounters where presenting symptom prompted evaluation leading to Hodgkin lymphoma diagnosis, sequence the confirmed cancer code first once diagnosis is established.
- Treatment encounter sequencing: When encounter is solely for chemotherapy or radiation therapy administration, sequence Z51.11 (chemotherapy) or Z51.0 (radiation therapy) first, followed by C81.90.
- Multiple malignancy considerations: If patient has multiple primary cancers, sequence according to the focus of the encounter or treatment being provided.
Real-World Coding Scenario — How C81.90 Is Applied in Practice
A 34-year-old patient presents to medical oncology for initial consultation following biopsy at an outside hospital two weeks prior. The referring physician’s note states “patient has Hodgkin lymphoma per biopsy” and includes a brief pathology report summary indicating “lymph node biopsy positive for Hodgkin lymphoma with Reed-Sternberg cells present.” The pathology report does not specify whether the subtype is classical Hodgkin lymphoma (nodular sclerosis, mixed cellularity, lymphocyte-rich, or lymphocyte-depleted) or nodular lymphocyte-predominant type. The medical oncologist documents a comprehensive visit discussing staging workup, treatment options, and prognosis for “Hodgkin lymphoma, type unspecified per outside pathology.” Staging PET/CT ordered but not yet completed at time of this visit.
Correct Code Application
- Primary diagnosis code: C81.90 — Documentation confirms Hodgkin lymphoma but neither subtype nor specific anatomic site can be determined from available records
- CPT code: 99204 or 99205 — New patient office visit, medical oncology consultation
- Rationale: Pathology confirms Hodgkin lymphoma diagnosis but lacks detail needed for specific subtype coding; oncologist’s documentation appropriately acknowledges unspecified status; staging workup pending
Common Mistake in This Scenario
- Incorrect code selection: Using C81.10 (nodular sclerosis Hodgkin lymphoma, unspecified site) based on assumption that “most Hodgkin cases are nodular sclerosis”
- Why this fails: Coders cannot assign specific subtypes based on statistical likelihood or clinical assumptions; code assignment must reflect actual documented findings
- Audit risk: Selecting a specific subtype code without supporting pathology documentation exposes the practice to allegations of upcoding and false claims
- Correct approach: Assign C81.90 and submit compliant query to oncologist asking whether full pathology report contains subtype detail not included in the consultation note
Frequently Asked Questions About ICD-10 Code C81.90
Is ICD-10 Code C81.90 Still Valid for Use in 2026?
ICD-10 code C81.90 remains a valid, billable diagnosis code for fiscal year 2026 with no changes to its description or validity status since its introduction in October 2015. The code became effective on October 1, 2025 for the 2026 fiscal year and will remain valid through September 30, 2026.
What Is the Difference Between C81.90 and C85.90?
C81.90 is used for Hodgkin lymphoma when subtype and site are unspecified, while C85.90 designates Non-Hodgkin lymphoma, unspecified, unspecified site. These represent fundamentally different disease entities; Hodgkin lymphoma is characterized by Reed-Sternberg cells and follows different treatment protocols than Non-Hodgkin lymphoma.
Can I Use C81.90 for a Patient in Remission?
No, C81.90 should not be used for patients documented as being in remission. When documentation explicitly states the patient is in remission, assign code C81.9A (Hodgkin lymphoma, unspecified, in remission) instead. For patients who completed treatment years ago with no active disease, use personal history code Z85.71.
What Documentation Is Absolutely Required to Support C81.90?
The medical record must contain pathology or biopsy results confirming Hodgkin lymphoma diagnosis, typically showing Reed-Sternberg cells or explicit pathologist statement of Hodgkin lymphoma. Without objective pathology confirmation, C81.90 cannot be assigned regardless of clinical suspicion documented in provider notes.
How Does C81.90 Affect Medicare Reimbursement?
C81.90 impacts Medicare reimbursement through MS-DRG assignment in inpatient settings, grouping claims into lymphoma-specific DRGs 820-825 or 840-842 depending on procedures and complications. The code also affects Hierarchical Condition Category risk adjustment in Medicare Advantage plans, potentially influencing capitated payment rates to healthcare organizations.
Should I Query the Provider When Using C81.90?
Query the provider when clinical documentation suggests more specific information may be available but is not clearly stated in the record. If oncology notes discuss specific subtypes or radiology identifies particular lymph node regions but pathology report does not match, submit a compliant query asking for clarification before defaulting to the unspecified code.
Is C81.90 Acceptable for Outpatient Office Visits?
Yes, C81.90 is appropriate for outpatient encounters when documentation supports Hodgkin lymphoma diagnosis but lacks subtype or site specificity. This commonly occurs during initial oncology consultations, treatment planning visits, or follow-up appointments when historical records contain limited detail from outside facilities.
Key Takeaways
Understanding C81.90 requires balancing appropriate use of unspecified codes with the imperative to maximize coding specificity whenever documentation supports more detailed alternatives:
- C81.90 designates Hodgkin lymphoma when subtype and anatomic site cannot be determined from available documentation
- Pathology confirmation showing Reed-Sternberg cells or explicit Hodgkin lymphoma diagnosis is mandatory for code assignment
- Never use C81.90 when documentation specifies nodular sclerosis, mixed cellularity, lymphocyte-rich, or other recognized subtypes
- Distinguished from C81.9A (remission) and Z85.71 (personal history) based on current disease status
- Appropriate physician queries prevent under-coding when chart suggests additional specificity may be available
- DRG impact and payer audit patterns make solid documentation support essential for claim defense
- Annual verification against updated ICD-10-CM Official Coding Guidelines ensures continued compliant use
For additional guidance on oncology coding best practices and documentation requirements, consult the American Health Information Management Association Coding Clinic advisories and CMS ICD-10-CM Official Guidelines for Coding and Reporting published annually.