Etiology and Pathophysiology of Malignant Ascites

The American Society of Clinical Oncology notes that gastric cancer peritoneal metastasis is a significant cause of malignant ascites, accounting for between one-fifth and three-fifths of all metastatic recurrences after gastrectomy 2
Lobular breast cancer has a unique propensity to metastasize to the peritoneum, similar to gastric cancer, due to specific molecular characteristics 1
Epithelial-mesenchymal transition (EMT) is a critical process where epithelial cells transform into a mesenchymal phenotype with increased migratory and invasive capabilities, according to the American Association for Cancer Research 1
Primary gastric tumors of the EMT subtype develop peritoneal metastasis more frequently and have worse prognosis compared to non-EMT subtypes 1

Genomic Drivers and Paracrine Factors

The National Comprehensive Cancer Network states that TP53 mutations occur at similar rates in peritoneal metastases as in primary tumors, while CDH1 mutations are more frequent, particularly in diffuse-type gastric cancers 1, 4
Novel drivers such as PIGR and SOX9 have been identified in tumor cells derived from malignant ascites, as reported by the American Society of Clinical Oncology 1, 4
Malignant ascites contains various growth factors, cytokines, chemokines, and other soluble factors that create a tumorigenic environment, according to the European Association for the Study of the Liver 1, 6

The American Association for the Study of Liver Diseases recommends that ascitic fluid cytology is positive only in the setting of peritoneal carcinomatosis with a sensitivity of 96.7% if three samples are sent and processed promptly 8, 9
The first cytology sample is positive in 82.8% of cases and at least one of two samples is positive in 93.3%, as stated by the American Association for the Study of Liver Diseases 8