Biopsy-Resection Agreement of Peritoneal Histopathological Growth Patterns in Colorectal Peritoneal Metastases: A Prospective Observational Pilot Study

his prospective, single-center observational pilot study evaluates whether peritoneal histopathological growth patterns can be assessed on limited excisional biopsies obtained during staging laparoscopy in adults with suspected or confirmed colorectal peritoneal metastases. The study primarily evaluates agreement between the dominant histopathological growth pattern identified on laparoscopic biopsy and that identified on subsequent operative specimens. One to three peritoneal deposits will be sampled during staging laparoscopy. When surgery proceeds, up to three peritoneal deposits will be collected from the operative specimen, preferably from corresponding Peritoneal Cancer Index regions. Two pathologists, blinded to clinical information, specimen timing, and each other's assessments, will independently estimate the proportions of pushing and infiltrating growth patterns. Histopathological growth pattern findings will not be used to guide clinical management. Biopsy evaluability, interobserver reproducibility, interlesional heterogeneity, and exploratory associations with clinical and surgical characteristics will also be assessed.

Inclusion Criteria: * Age ≥ 18 years * Histologically confirmed colorectal adenocarcinoma * Suspected or confirmed peritoneal metastases from colorectal cancer based on imaging or prior clinical evaluation * Patients undergoing staging laparoscopy and/or cytoreductive surgery (CRS) ± hyperthermic intraperitoneal chemotherapy (HIPEC) as part of standard clinical care * Availability of peritoneal metastasis tissue samples suitable for histopathological analysis * Written informed consent provided for participation in the study Exclusion Criteria: * Age \< 18 years * Peritoneal metastases originating from non-colorectal primary tumors * Absence of available or adequate peritoneal metastasis tissue samples for histological growth pattern analysis * Patients who decline or withdraw informed consent * Patients unable to provide informed consent