ICD-10-CM > C00-D49 > D10-D36 > D20 D20 Benign neoplasm of soft tissue of retroperitoneum and peritoneum Non-Billable/Non-Specific Type 1 Excludes benign lipomatous neoplasm of peritoneum and retroperitoneum (D17.79)benign neoplasm of mesothelial tissue (D19.-) Codes D20.0Benign neoplasm of soft tissue of retroperitoneumD20.1Benign neoplasm of soft tissue of peritoneum