Peritoneal Surface Malignancies - Characterization, Models and Treatment Strategies

This study is collecting tissue and fluid samples from patients with cancers that have spread to the lining of the abdomen (a condition called peritoneal surface malignancy) to better understand this type of cancer spread and develop new laboratory models that could lead to better treatments. **You may be eligible if...** - You have been diagnosed with a cancer that has spread to the peritoneum (the inner lining of the abdominal cavity), such as colorectal cancer, appendix cancer, ovarian cancer, or mesothelioma - You are scheduled for surgery or a procedure where abdominal tissue or fluid samples can be collected - You are willing to allow tissue and fluid samples to be used for research - You are at least 18 years old **You may NOT be eligible if...** - You are not scheduled for a procedure where samples can be safely obtained - You are unwilling to consent to sample collection for research purposes - Your overall health is too poor to safely undergo sample collection - You are pregnant Talk to your doctor to see if this trial is right for you.