What is Mesothelioma? Malignant mesothelioma (and mesothelioma) is a cancer that forms in the mesothelium, or the membrane of epithelial cells that surround the thoracic cavity, abdominal cavity, heart, and testes. Mesothelioma develops in the thin layers of tissue that surround the internal organs, called the mesothelium. The types of mesothelioma are named for the … Continue reading Mesothelioma Cancer