Non-Islet Cell Tumor Hypoglycemia at the Second Recurrence of Malignant Solitary Fibrous Tumor in the Retroperitoneum and Pelvis: A Case Report

An 83-year-old man underwent complete resection of a large malignant solitary fibrous tumor in the retroperitoneum in 2006 and of a local recurrent tumor in 2010. In 2011, he was admitted to our hospital because of hypoglycemia. His serum glucose level was very low, and his levels of insulin and C-peptide were low. Furthermore, he had a recurrent tumor in the retroperitoneum and pelvis. Immediately after the third surgery for complete resection, he had no hypoglycemic episodes and his serum glucose level was within the normal range. Immunoblotting analysis revealed a high-molecular-weight form of insulin-like growth factor II in the patient's serum and in the protein extract obtained from the resected specimen in 2011. To our knowledge, this is the first report of non-islet cell tumor hypoglycemia caused by a malignant solitary fibrous tumor secreting a high-molecular-weight form of insulin-like growth factor II at the second recurrence.