ICD-10 Code C48 – Malignant neoplasm of retroperitoneum and peritoneum (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C48 – Malignant neoplasm of retroperitoneum and peritoneum
What it is
C48 identifies a malignant tumor arising in the retroperitoneum or peritoneum. Use it when documentation states a primary cancer in these spaces and no more specific site code is available.
Clinical signs
Clinical features vary; refer to documentation. Patients may present with abdominal or pelvic mass, pain, bloating, or findings from imaging or biopsy confirming malignant disease in the retroperitoneal or peritoneal region.
When to use this code
Use C48 when the provider documents a primary malignant neoplasm of the retroperitoneum or peritoneum. It also fits cases where pathology, imaging, or operative notes support a malignant tumor in that anatomic area. If the record names a more specific site, code that instead.
Do not use for
Do not use C48 for metastatic disease to the peritoneum or retroperitoneum unless the provider identifies a primary tumor there. Check documentation when the site is uncertain or when the malignancy is described more specifically elsewhere.
Coding tip
Confirm whether the tumor is primary, secondary, or unspecified before assigning C48.