C79.2 (Secondary malignant neoplasm of skin) compared with D04.9 (Carcinoma in situ of skin, unspecified), from the official CMS tabular data. C79.2 and D04.9 name the same anatomical site (connective tissue) with a different neoplasm behavior. MedCoder-derived
Same anatomical site, different neoplasm behavior.
Same site — carcinoma in situ (connective tissue)
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. C79.2 and D04.9 name the same anatomical site (connective tissue) 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.
| C79.2Secondary malignant neoplasm of skin | D04.9Carcinoma in situ of skin, unspecified | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | C00-D49 — Neoplasms (C00-D49) | C00-D49 — Neoplasms (C00-D49) |
| Definition | Secondary malignant neoplasm of skin is a billable ICD-10-CM diagnosis code (C79.2). | Carcinoma in situ of skin, unspecified is a billable ICD-10-CM diagnosis code (D04.9). |
| Includes | — | Bowen's disease erythroplasia grade III intraepithelial neoplasia Queyrat's erythroplasia |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources