Mechanisms of peritoneal metastasis formation

Abstract

Mechanisms of peritoneal metastasis (PM) formation remain unclear. It has long been considered that the establishment of PM is a multi-step process. Here are the recent new concepts of the formation of PM, in terms of three patterns of PM: trans-mesothelial, trans-lymphatic, and superficial growing metastasis. Trans-mesothelial metastasis is established through detachment of cancer cells, adhesion on distant peritoneal surface, invasion into submesothelial tissue, and proliferation. Trans-lymphatic metastasis develops by the migration of peritoneal free cancer cells (PFCCs) into omental milky spots and/or initial lymphatic vessels. Superficial growing metastasis is established by growing of PFCCs on the peritoneal surface after trapping or adhesion to pocket-like structure or pouch in pelvic cavity or in peritoneum absorbed by negative pressure generated omental milky spots or initial lymphatic vessels. Trans-mesothelial and trans-lymphatic metastasis are found in high-grade carcinomas, such as gastric, colorectal, ovarian, gall bladder, and pancreas caner. In contrast, superficial growing metastasis is found in PM from appendiceal mucinous neoplasm, mesothelioma, granulosa cell tumor, multicystic mesothelioma, and hepatoma. Surgeons should perform peritonectomy in accordance with the metastatic pattern and biological behavior of each tumor.