A Case of Nonislet Cell Tumor Hypoglycemia Due to Metastatic Salivary Myoepithelial Carcinoma

Nonislet cell tumor hypoglycemia (NICTH) is an uncommon cause of hypoglycemia due to a relative surplus of insulin-like growth factor 2 (IGF-2) or its precursor molecule. The diagnosis is confirmed by an elevated ratio of IGF-2 to insulin-like growth factor 1 (IGF-1). Myoepithelial carcinoma (MECA) is a rare and aggressive salivary gland cancer that has not been previously associated with NICTH.

A 63-year-old female with a past medical history of metastatic salivary MECA, type 2 diabetes mellitus previously on metformin, hypertension, and hypothyroidism presented to her oncologist for chemotherapy and was found to have a serum glucose of 30 mg/dL (reference: 65-99). She was admitted for further diagnostic work-up which revealed an insulin level of <1 μU/mL (reference: 3-25), C-peptide <0.5 ng/mL (reference: 1.1-4.3), IGF-1 of 15 ng/mL (reference: 41-279), and IGF-2 of 147 ng/mL (reference: 180-580) with an IGF-2:IGF-1 molar ratio of 10, consistent with NICTH. The patient's hypoglycemia unfortunately was quite resistant to treatment, requiring a combination of corticosteroids, continuous dextrose infusion, and somatostatin injections. The patient died 3 weeks after presenting with hypoglycemia.

Salivary MRCAs commonly contain pleomorphic adenoma gene 1 oncogene rearrangements which are associated with increased IGF-2 production and may predispose patients to hypoglycemia.

This case demonstrates that NICTH can be associated with metastatic salivary MECA. The hypoglycemia in this scenario is challenging to manage and is associated with poor prognosis.