ICD-10 Code C48.8 – Malignant neoplasm of overlapping sites of retroperitoneum and peritoneum (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C48.8 – Malignant neoplasm of overlapping sites of retroperitoneum and peritoneum
What it is
C48.8 identifies a malignant tumor that involves overlapping sites of the retroperitoneum and peritoneum. Use it when the primary cancer site spans both areas and a more specific location is not documented.
Clinical signs
Clinical features vary; refer to documentation. Patients may have abdominal or pelvic mass, pain, bloating, or nonspecific pressure symptoms, but the code is assigned from the documented anatomic site, not symptoms alone.
When to use this code
Use C48.8 when the provider documents a primary malignancy arising in, or involving, overlapping retroperitoneal and peritoneal sites. It is appropriate when the record does not support a single more specific subsite. Verify whether the neoplasm is primary, secondary, or metastatic before coding.
Do not use for
Do not use this code for a tumor confined to only the retroperitoneum or only the peritoneum. Do not apply it to benign, uncertain, or metastatic disease unless the documentation specifically supports a primary malignant neoplasm.
Coding tip
Check the pathology and operative note for the exact anatomic origin before selecting C48.8.