Hypoglycemia in the Setting of Advanced Gastrointestinal Stromal Tumor

We report a rare case of symptomatic hypoglycemia in a patient with intra-abdominal recurrence of a previously resected gastrointestinal stromal tumor (GIST). The patient is a 65-year-old woman who underwent resection of a large abdominal mass arising from the stomach, histologically diagnosed as a high-grade leiomyosarcoma. She was lost to follow up. Five years later, the mass recurred; core biopsy demonstrated a CD 117-positive, spindle-cell tumor, consistent with a GIST. She was placed on Gleevec, as there was evidence of multifocal disease, but imaging revealed only mild improvement. Subsequently, her clinical status deteriorated, and she was hospitalized for dehydration, vomiting, and mental status changes. Her blood glucose on admission was 22 mg/dL, and a dextrose infusion (50%) was necessary to maintain adequate blood glucose levels. Measurements of insulin, proinsulin, c-peptide, β-hydroxybutyrate, and thyroid-stimulating hormone were normal, as were cosyntropin stimulation and glucagon response tests. Suspicions arose for tumor-secreted insulin-like factor. She underwent resection of the dominant 44-cm recurrence, with immediate rebound hyperglycemia, followed by complete normalization of her blood glucose levels. She was discharged on postoperative Day 5 without symptoms or insulin, and is alive with disease at 20 months. Paraneoplastic syndromes occur in only 15 per cent of patients with known malignancies (e.g., lung cancer and metastatic carcinoid), and are rarely reported in the setting of GIST. Hypoglycemia is most often observed in presence of insulinoma and only isolated case reports in GIST patients exist. Overexpression of insulin-like growth factor II is thought to be the mechanism of action. Supportive management and palliative resection or debulking is recommended when possible.