ICD-10 C37
Billable / Specific HCC v28: 11 CCMalignant neoplasm of thymus
About ICD-10-CM C37
ICD-10-CM code C37 represents Malignant neoplasm of thymus. This is a billable/specific code in the Neoplasms chapter (block C37). The 2026 edition of ICD-10-CM C37 became effective on October 1, 2025.
Coding Tips for C37
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
C37 is a CMS-HCC v28 risk-adjustment code (category 11). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
C37 is designated CC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-CC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag CC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Type 1 Excludes
Pure excludes, these codes can never be coded together with C37. The conditions are mutually exclusive (e.g., congenital vs acquired forms).
- malignant carcinoid tumor of the thymus (C7A.091)
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Inpatient DRG Impact, CC
codes Malignant neoplasm of thymus. As a Complication/Comorbidity (CC), this contributes to DRG severity adjustment when documented alongside the principal diagnosis.
Medicare LCD Coverage for C37
Local Coverage Determinations (LCDs) from CMS MACs that list C37 as a covered diagnosis.
Showing top 10 of 745 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing C37.
1 Aetna
2 Cigna
5 Medicare
CPT Codes Commonly Billed with C37
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- J2353 CMS LCD: Billing and Coding: Octreotide Acetate for Injectable Suspension (Sandostatin� LAR Depot) CMS LCD
Convert C37 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| C37 | 1640 | 00000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To C37
Other codes in section C30-C39 (Malignant neoplasms of respiratory and intrathoracic organs).
ICD-10 C37, Billing FAQ
Is ICD-10 code C37 billable? +
Yes, C37 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What codes are Type 1 Excludes for C37? +
Type 1 Excludes (never code together with C37): malignant carcinoid tumor of the thymus (C7A.091)
Does C37 affect Medicare Advantage HCC risk adjustment? +
Yes. C37 maps to CMS-HCC v28 category 11. Capture this diagnosis annually for accurate Medicare Advantage risk score.
Is C37 a CC or MCC for inpatient DRG? +
Yes, this code is designated as CC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with C37? +
Procedures frequently paired with C37 include: J2353.
What ICD-9 codes does C37 map to? +
Per CMS GEMs, C37 maps to ICD-9 codes: 1640. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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