Giant Solitary Fibrous Tumor Associated with Loss of Consciousness by Hypoglycemic Attack

: We herein report a rare case of solitary fibrous tumor (SFT) producing high-molecular-weight insulin-like growth factor Ⅱ(big IGF-Ⅱ). A 51-year-old woman with a large mass in the right thorax suffered from repeated loss of consciousness due to hypoglycemic attack. A hematological examination revealed low values of serum insulin and C-peptide despite her hypoglycemia. We therefore regarded her giant thoracic tumor as the cause of the hypoglycemic attack. She underwent resection of the tumor and was diagnosed with SFT pathologically. After the surgery, her blood sugar level stabilized immediately, and she has had no hypoglycemic attacks since. Although we identified big IGF-Ⅱ in a preoperative serum sample by a Western immunoblot analysis, it was not detected after surgical resection. Positivity for big IGF-Ⅱ was observed in the tumor cells by immunohistochemical staining. We therefore concluded that big IGF-Ⅱ produced by the SFT caused the hypoglycemic attack in this patient.