Abstract #1402832: Doege-Potter Syndrome Due to Solitary Fibrous Tumor of the Kidney

Abstract

Solitary fibrous tumor (SFT) is a rare mesenchymal tumor which can be benign or malignant. A small subset (<5%) of patients with SFT present with refractory hypoglycemia, known as Doege-Potter syndrome. This is due to increased production of insulin-like growth factor (IGF-2), its precursor pro-IGF-2, and is associated with large tumor size or aggressive clinical behavior. A 77-year-old female was brought to the ER after was found down at home with hypoglycemia down to 20 mg/dL during a wellness check. She had slurred speech and right-sided weakness. MRI of the brain and MRA of head and neck were unremarkable. She was found to have a urinary tract infection which was treated with antibiotics. Due to concern for stroke, aspirin was started. Subsequently she developed hematuria. A CT abdomen and pelvis was performed that revealed a large 17 x 12 x 11 cm heterogenous exophytic mass from the anterior margin of the right kidney. Patient's encephalopathy and focal weakness resolved with glucose administration, but she continued to have recurrent hypoglycemic episodes. A repeat MRI of the brain showed no evidence of metastatic disease and no evidence of CVA. Thyroid, adrenal and liver function tests were within normal range, and insulin and C-peptide levels were grossly suppressed during hypoglycemic episodes. IGF-1 and IGF-2 levels were normal. In the absence of any underlying endocrine pathology or the administration of any hypoglycemic agent, clinically Whipple’s triad was positive (symptoms attributable to hypoglycemia, plasma hypoglycemia at time of symptoms and resolution of symptoms with treatment of hypoglycemia). Tumor induced hypoglycemia was suspected and she underwent right radical nephrectomy. Pathology demonstrated a fully resected large (21 x 11.5 x 11 cm) spindle cell neoplasm, positive for CD34 and STAT6, consistent with solitary fibrous tumor. Post-surgically her hypoglycemia resolved. Our case highlights the importance of early diagnosis and intervention in Doege-Potter syndrome. Hypoglycemia with low levels of serum insulin, C-peptide, and beta-hydroxybutyrate in a healthy-appearing person should prompt evaluation for a tumor with cross-sectional imaging of the chest, abdomen, and pelvis. Although our patient had normal IGF-2 levels, pro-IGF-2 levels were not checked. In SFT the hypoglycemia may be due to elevated IGF-2 or pro-IGF-2 levels which leads to inappropriate activation of systemic insulin receptors and inhibition of glucose release from the liver leading to fatal hypoglycemia. Tumor induced hypoglycemia should be considered as the primary differential diagnosis when hypoglycemia is without an alternative cause.