Solitary fibrous tumor of the uterus producing high-molecular-weight insulin-like growth factor II and associated with hypoglycemia.

We report a case of solitary fibrous tumor of the uterus producing high-molecular-weight insulin-like growth factor II (big IGF-II). A 78-year-old woman presented with a massive uterine tumor and worsening hypoglycemia. Endocrine and metabolic investigations revealed that her serum contained big IGF-II. Pathologic examination of the myometrial tumor showed spindle cells separated by thick collagen fibers. The tumor cells were immunoreactive for CD34 and IGF-II (inclusive of big IGF-II) but not smooth muscle actin or desmin. Postoperatively the hypoglycemia and the serum big IGF-II disappeared with recovery of suppressed insulin and growth hormone levels. Western blotting of the tumor extract revealed the presence of big IGF-II, the molecular weight of which was similar to that of aberrant serum IGF-II. To our knowledge, this is the first case of uterine solitary fibrous tumor.