Mesothelioma Cancer

Features of malignant mesothelioma

Pathology (disease features)

Malignant mesothelioma develops in the mesothelial cells that form the pleura, the peritoneum, and coverings of other organs. Most cases arise in the pleura, the thin membrane that covers the lungs and lines the chest wall; right-sided involvement is more common. In these cases, malignant mesotheliomas first look like multiple, tiny, round, gray, flat or slightly raised spots on the pleura. These spots fuse together over time, so that the pleural surface becomes progressively thicker and bumpy. The tumor spreads in all directions, forming a continuous thick, soft, 'rind' encasing the lung, and contracting it.

As the tumor advances, other nearby organs are invaded, including the lungs themselves, chest wall, the mediastinum and its structures, and ribs. There may be direct invasion through the diaphragm into the abdominal cavity, and so to the liver. In many cases, the tumor may also grow along wounds or tracts left by diagnostic or therapy procedures; this can be avoided by the use of radiation therapy at the time of the procedure.

Eventually, there may be distant spread to other parts of the body (metastases). These are found in 50% of autopsy cases, but usually don't cause any symptoms.