C48.1 (Malignant neoplasm of specified parts of peritoneum) compared with D48.4 (Neoplasm of uncertain behavior of peritoneum), from the official CMS tabular data. C48.1 and D48.4 name the same anatomical site (cul-de-sac) with a different neoplasm behavior. MedCoder-derived
Same anatomical site, different neoplasm behavior.
Same site — uncertain behavior (cul-de-sac)
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. C48.1 and D48.4 name the same anatomical site (cul-de-sac) 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.
| C48.1Malignant neoplasm of specified parts of peritoneum | D48.4Neoplasm of uncertain behavior of peritoneum | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | C00-D49 — Neoplasms (C00-D49) | C00-D49 — Neoplasms (C00-D49) |
| Definition | Malignant neoplasm of specified parts of peritoneum is a billable ICD-10-CM diagnosis code (C48.1). | Neoplasm of uncertain behavior of peritoneum is a billable ICD-10-CM diagnosis code (D48.4). |
| Includes | Malignant neoplasm of cul-de-sac Malignant neoplasm of mesentery Malignant neoplasm of mesocolon Malignant neoplasm of omentum | — |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources