The distribution of cancer cells in the abdominal cavity is partly exposed to gravity and partly follows the current of the peritoneal fluid.
- Gravity creates an accumulation of cells in the pelvis with growth in the peritoneum on the Peritoneal fossa
- The peritoneal fluid is reabsorbed on the diaphragm and the large and small omentums and in the paracolic ducts. The accumulated cells under the diaphragm attaches easily to the liver, gallbladder, and surface of the spleen . Tumor in the small omentum often grows on the gastric antrum.
Malignant cells of high and moderate differentiation attach themselves to the mobile small intestine usually only in an advanced stage . In more malignant cases, the cells may attach to larger parts of the small intestine.
The thickness of the peritoneal tumor can vary from microscopic to several centimeters.
- In DPAM (disseminated peritoneal adenomucinosis), the tumor grows on the peritoneum without infiltrating the underlying tissue and the peritoneum is separated relatively easily when there is no pre-tumoral inflammation.
- With infiltrating growth, the tumor attaches to underlying tissue, which must be resected together with the tumor. Infiltrating gowth may be impossible to differentiate from pseudoinfiltration when mucous infiltrates into the scar tissue.
Lymph nodes and distant metastases
- Pseudomyxoma of the DPAM type does not spread to the lymph nodes hematogenously.
- Apparent benign mesothelioma may to some degree spread to lymph nodes or hematogenously.
- The more malignant a tumor appears to be, the larger the tendency for dissemination to lymph nodes and other organs.