[A case of retroperitoneal solitary fibrous tumor associated with hypoglycemia].

Solitary fibrous tumor is an uncommon mesenchymal lesion, seldom associated with hypoglycemia and rarely presents as a retroperitoneal tumor. We present a case in a 56-year-old male patient whose initial symptom was unconsciousness due to hypoglycemia (blood glucose 16 mg/dl). Computed tomography indicated a mass (about 20 x 15 x 15 cm) in the retroperitoneum. Only surgical treatment was performed and the patient has been without hypoglycemia and recurrence for 12 months after surgery. This case had "patternless pattern" characterized by a haphazard, storiform arrangement of short spindle or ovoid cells, and "hemangiopericytoma-like appearance" with prominent vascularity by thin-walled vessels, as expressed CD34 immunohistochemically. Pathohistological examination revealed increased cellularity in the tumor tissues as well as tissues with atypical nuclei of the tumor cells with some cell division. Western immunoblotting and immunohistochemistry showed that tumor produced big IGF-II, leading to hypoglycemia. Due to these findings, it was diagnosed as malignant solitary fibrous tumor associated with non-islet cell tumor hypoglycemia (NICTH). This case is the second malignant solitary fibrous tumor in the retroperitoneum with hypoglycemia in the English literature.