C37 Malignant neoplasm of thymus

The ICD-10-CM code for Malignant neoplasm of thymus is C37 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

2: Neoplasms (C00-D49)

Section

C30-C39: Malignant neoplasms of respiratory and intrathoracic organs (C30-C39)

Category C37

1 code (1 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to C37:

• Thymoma › sclerosing
• Carcinoma (malignant) › thymic
• Thymoma › type A
• Thymoma › metaplastic
• Thymoma › type B2
• Thymoma › type AB
• Thymoma › malignant
• Thymoma › type B1

U.S. Hospital Utilization

• An estimated 3,775 U.S. inpatient stays in 2023 included C37 among the documented diagnoses.
• 2,110 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Tx of primary site (TOC entry)

a. Admission/Encounter for treatment of primary site ............................................................. 33

Tx of secondary site (TOC entry)

b. Admission/Encounter for treatment of secondary site .......................................................... 33

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)