Approximately 5% of patients with solitary fibrous tumors outside the pleura exhibit hypoglycemia, which may be caused by the large amount of insulin-like growth factor II (IGF II) produced by the tumor; such a manifestation is referred to as Doege-Potter syndrome[10], and 12–13% of patients with this syndrome suffer from malignant solitary fibrous tumors. The gene discussed is IGF2; the disease is Hypoglycemia.