Malignant neoplasm of thymus (C37) ICD-10-CM
The C37 code range covers malignant neoplasm of thymus with 1 ICD-10-CM diagnosis codes. 1 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
- malignant carcinoid tumor of the thymus C7A.091
Codes in the C37 Range 1 codes · 1 billable
- C37 Malignant neoplasm of thymus
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the C37 range.
Thymoma
A neoplasm originating from thymic tissue, usually benign, and frequently encapsulated. Although it is occasionally invasive, metastases are extremely rare. It consists of any type of thymic epithelial cell as well as lymphocytes that are usually abundant. Malignant lymphomas that involve the thymus, e.g., lymphosarcoma, Hodgkin's disease (previously termed granulomatous thymoma), should not be regarded as thymoma. (From Stedman, 25th ed)
About the C37 Code Range
The ICD-10 code C37 is specifically used to identify a malignant neoplasm of the thymus, a rare type of cancer found in the thymus gland located in the chest. This code is essential for documenting and classifying various malignant thymic tumors.
Commonly referred to by terms such as thymoma type A, B, or AB, primary malignant thymoma, or thymic epithelial neoplasm, these synonyms help clarify the many forms malignancies of the thymus can take. The code also covers detailed staging descriptions, from stage I tumors confined to the thymus to advanced stages (IVa and IVb) involving spread to surrounding tissues or dissemination through pleural, pericardial, hematogenous, or lymphatic routes. Additionally, C37 includes less common types like primary small cell neuroendocrine carcinoma of the thymus and primary thymic carcinoma. Understanding these synonyms and stages assists medical coders and healthcare professionals in accurately coding conditions such as malignant thymoma and neuroendocrine carcinoma using the ICD-10 code for malignant neoplasm of the thymus. This precise classification supports appropriate diagnosis, treatment planning, and research.
Questions About This Page
How many billable codes are in the C37 range?
Of the 1 codes in this range, 1 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the C37 range classify?
The range classifies malignant neoplasm of thymus. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
