C01 (Malignant neoplasm of base of tongue) compared with C79.89 (Secondary malignant neoplasm of other specified sites), from the official CMS tabular data. C01 and C79.89 name the same anatomical site (tongue) with a different neoplasm behavior. MedCoder-derived
Same anatomical site, different neoplasm behavior.
Same site — secondary malignancy (tongue)
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. C01 and C79.89 name the same anatomical site (tongue) 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.
| C01Malignant neoplasm of base of tongue | C79.89Secondary malignant neoplasm of other specified sites | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | C00-D49 — Neoplasms (C00-D49) | C00-D49 — Neoplasms (C00-D49) |
| Definition | Malignant neoplasm of base of tongue is a billable ICD-10-CM diagnosis code (C01). | Secondary malignant neoplasm of other specified sites is a billable ICD-10-CM diagnosis code (C79.89). |
| Includes | Malignant neoplasm of dorsal surface of base of tongue Malignant neoplasm of fixed part of tongue NOS Malignant neoplasm of posterior third of tongue | — |
| Use additional code | code to identify: alcohol abuse and dependence (F10.-) history of tobacco dependence (Z87.891) | — |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources