Malignant neoplasm of thymus
In Malignant neoplasms of respiratory and intrathoracic organs (C30-C39), chapter 2: Neoplasms
- C37 is billable and valid on claims for FY 2027. If the record has more detail, check the other codes under C30-C39 below.
- As a secondary diagnosis it is a CC (complication or comorbidity), which can raise the MS-DRG payment. It doesn't count when the principal diagnosis is one of 2 closely related codes.
- Counts toward HCC 21 (Lymphoma and Other Cancers) in the Medicare Advantage risk model (CMS-HCC V28).
- AHRQ's Chronic Condition Indicator classes it as chronic: expected to last 12 months or longer and to limit daily life or need ongoing care.
- 365 US deaths in 2024 had an underlying cause in category C37, per the National Vital Statistics System on CDC WONDER. Death records use WHO ICD-10, so the count is for the whole category.
Also indexed as: Carcinoma, thymic; Thymoma, malignant; Thymoma, metaplastic; Thymoma, sclerosing; Thymoma, type A; Thymoma, type AB; Thymoma, type B1; Thymoma, type B2; Thymoma, type B3
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Instructional notes
Excludes1: not coded here, use a different code
- malignant carcinoid tumor of the thymus (C7A.091)
Also applies, from Malignant neoplasms of respiratory and intrathoracic organs (C30-C39)
These notes sit on C30-C39 and apply to every code under it, including C37.
Includes: conditions that are coded here
- malignant neoplasm of middle ear
Excludes1: not coded here, use a different code
- mesothelioma (C45.-)
Official coding guidelines
From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.
Rules for coding benign and malignant neoplasms: using the Neoplasm Table, sequencing primary and secondary sites, treatment encounters, complications, and current cancer versus personal history.
- Admission/Encounter for treatment of primary site (page 33)
- Admission/Encounter for treatment of secondary site (page 33)
- Coding and sequencing of complications (page 34)
- Primary malignancy previously excised (page 34)
- Admissions/Encounters involving antineoplastic chemotherapy, immunotherapy and radiation therapy (page 35)
- Admission/encounter to determine extent of malignancy (page 36)
- Symptoms, signs, and abnormal findings listed in Chapter 18 associated with neoplasms (page 36)
- Admission/encounter for pain control/management (page 36)
Other codes under C30-C39
Malignant neoplasms of respiratory and intrathoracic organs (C30-C39)
- C30Malignant neoplasm of nasal cavity and middle ear
- C31Malignant neoplasm of accessory sinuses
- C32Malignant neoplasm of larynx
- C33Malignant neoplasm of trachea
- C34Malignant neoplasm of bronchus and lung
- C37Malignant neoplasm of thymus(this code)
- C38Malignant neoplasm of heart, mediastinum and pleura
- C39Malignant neoplasm of other and ill-defined sites in the respiratory system and intrathoracic organs
C37 MS-DRGs
As the principal diagnosis, C37 groups to these 8 MS-DRGs (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.
- DRG 826 Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures with MCC
- DRG 827 Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures with CC
- DRG 828 Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures without CC/MCC
- DRG 829 Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Other Procedures with CC/MCC
- DRG 830 Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Other Procedures without CC/MCC
- DRG 843 Other Myeloproliferative Disorders or Poorly Differentiated Neoplastic Diagnoses with MCC
- DRG 844 Other Myeloproliferative Disorders or Poorly Differentiated Neoplastic Diagnoses with CC
- DRG 845 Other Myeloproliferative Disorders or Poorly Differentiated Neoplastic Diagnoses without CC/MCC
Related conditions
Grouped by AHRQ's Clinical Classifications Software Refined (CCSR), which sorts every diagnosis code into clinically meaningful categories.
C37 is in Endocrine system cancers - thymus (NEO052, its default category), with 1 code.
Medicare coverage articles listing C37
These 27 Medicare billing and coding articles list C37 as a diagnosis that supports medical necessity for the services they cover. From the CMS Medicare Coverage Database; check your own contractor's article before billing.
- MolDX: Genetic Testing for Hereditary Thrombophilia (4 contractors)
- MolDX: Minimal Residual Disease Testing for Solid Tumor Cancers (4 contractors)
- MolDX: Next-Generation Sequencing for Solid Tumors (4 contractors)
- MolDX: Non-Next Generation Sequencing Targeted Molecular Panel Tests for Targeted Therapy in Cancer (4 contractors)
- MolDX: Plasma-Based Genomic Profiling in Solid Tumors (4 contractors)
- MolDX: Lab-Developed Tests for Inherited Cancer Syndromes in Patients with Cancer (3 contractors)
- MolDX: bioTheranostics Cancer TYPE ID® Update (3 contractors)
- Erythropoiesis Stimulating Agents (2 contractors)
- Lab: Flow Cytometry (2 contractors)
- Peripheral Nerve Blocks (2 contractors)
And 17 more.
Other codes that refer to C37
Notes on these codes point to C37.
About the condition
Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.
Thymus Cancer
The thymus is a small organ in your upper chest, under your breastbone. Before birth and during childhood, the thymus helps the body make a type of white blood cell. These cells help protect you from infections.
Read more about thymus cancer on MedlinePlusCode history
Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.
ICD-9-CM equivalent
Legacy crosswalk from the CMS General Equivalence Mappings (last updated 2018).
- 164.0 Malignant neoplasm of thymus