Peritoneal metastases found in routinely resected specimens after cytoreductive surgery and heated intraperitoneal chemotherapy

Introduction: Peritoneal metastases (PM) originating from colorectal cancer (CRC) and pseudomyxoma peritonei (PMP) can be treated with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Certain sites in the peritoneal cavity are prone to contain PM and are, therefore, routinely resected. The aim of this study is to investigate the frequency of disease in CRS specimens routinely resected. Secondly, to investigate if the risk of finding PM in routinely resected specimen is associated with involvement of anatomic related peritoneal areas. Materials and methods: This study investigated 433 patients diagnosed with PMP (n = 119) or PM from CRC (n = 314) and operated with CRS + HIPEC between June 2006 and November 2020 at a national center. Baseline data were prospectively registered. Pathology reports were reviewed for the presence of metastases in the routinely resected umbilicus, ligamentum teres hepatis, ovaries and greater omentum. Tumor extent was estimated using the Dutch region count. Results: PM was found in 14.7% of umbilical resections, in 17.4% of the resected ligamentum teres hepatis, in 48.2% of the resected ovaries and in 49.5% of the greater omentum specimens. We found an association between macroscopic disease involvement of the nearest region and risk of PM found in the related resections. Seven of 31 women with no macroscopically visible disease in the pelvis had PM diagnosed in the resected ovaries. Conclusions: A substantial proportion of routine resections held histologic verified PM. Our results may advocate for a routinely performed resection of the umbilicus, ligamentum teres hepatis, ovaries and greater omentum.