C37 (Malignant neoplasm of thymus) compared with D49.89 (Neoplasm of unspecified behavior of other specified sites), from the official CMS tabular data. C37 and D49.89 name the same anatomical site (thymus) with a different neoplasm behavior. MedCoder-derived
Same anatomical site, different neoplasm behavior.
Same site — primary malignancy (thymus)
The behavior documented for the site — malignant primary, secondary, carcinoma in situ, benign, uncertain or unspecified — decides which column of the neoplasm table, and therefore which code, applies.
Source: CMS Table of Neoplasms
Same site, different neoplasm behavior. D49.89 and C37 name the same anatomical site (thymus) with a different neoplasm behavior.
From the CMS/CDC Table of Neoplasms: the behavior documented for that site — malignant primary, secondary, carcinoma in situ, benign, uncertain or unspecified — decides which column, and therefore which code, applies.
| C37Malignant neoplasm of thymus | D49.89Neoplasm of unspecified behavior of other specified sites | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | C00-D49 — Neoplasms (C00-D49) | C00-D49 — Neoplasms (C00-D49) |
| Definition | Malignant neoplasm of thymus is a billable ICD-10-CM diagnosis code (C37). | Neoplasm of unspecified behavior of other specified sites is a billable ICD-10-CM diagnosis code (D49.89). |
| Includes | malignant neoplasm of middle ear | 'growth' NOS neoplasm NOS new growth NOS tumor NOS |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources