Peritoneal mesothelioma sufferers have been exposed to asbestos, the only known cause for this rare form of cancer. Located in the stomach lining, diagnoses are increasing as more asbestos-exposed workers from decades ago are noticing visible symptoms of the disease. The 20- to 40-year latency period that occurs from asbestos exposure to onset of visible symptoms has resulted in the rise of more patients in recent years.   Peritoneal mesothelioma is much less common than pleural mesothelioma. It accounts for about 10 to 20% of malignant mesothelioma cases. Symptoms of peritoneal mesothelioma include: stomach pain nausea and vomiting weight loss. Treatment for this cancer has improved significantly in the past years (especially when diagnosed early) and there are many promising trials and ongoing research.