The authors present a case of a 73 year old female patient. She had a left side pleural mesothelioma and had been operated thrice. At the third operation an abdominal propagation joined to the thoracic mesothelioma. Starting from this third surgery severe hypoglycemic episodes illustrated the clinical pictures. The electronmicroscopy of the resected tumor mass documented the presence of neurosecretory granules. This strongly suggests that tumor mass produced a substance which could have been responsible for the hypoglycemic episodes. Due to the fact the insulin levels measured during severe hypoglycemias were always on a low level, we suppose that an insulin like material (IGF--II) was responsible for the above mentioned symptoms. The authors briefly review the literature.