HYPERCALCEMIA OF MALIGNANCY IN A CASE OF PERIPHERAL NERVE SHEATH TUMOR: ELUCIDATING THE ROLES OF SIMULTANEOUS MECHANISMS.

ObjectiveHypercalcemia of malignancy (HCM) is caused by 1 of 5 known mechanisms including systemic release of ectopic parathyroid hormone (PTH)-related protein (PTHrP), calcitriol, PTH, cytokines, or destruction of bone by osteolytic metastases. We report the first case of 2 simultaneous mechanisms for HCM in a patient with a peripheral nerve sheath tumor (PNST).MethodsPubMed and Google Scholar searches were performed using "hypercalcemia of malignancy" as the search term.ResultsA 26-year-old woman with neurofibromatosis presented with worsening left hip pain. Magnetic resonance imaging showed a large left paraspinal mass, subtotal resection of which confirmed PNST. Despite chemo-radiation therapy, the tumor progressed over 16 months, requiring tumor debulking and L3-4 lumbar laminectomy. The patient developed progressive bilateral lower extremity weakness due to direct tumor invasion of the lumbosacral vertebrae with concurrent hypercalcemia. Ionized calcium was 1.47 mmol/dL (reference range is 0.95 to 1.32 mmol/dL), PTH was ConclusionHCM due to PTHrP and osteolytic metastases has not been independently reported to our knowledge in association with malignant PNST as in our patient. The therapeutic importance of characterizing the mechanism of HCM is further discussed in detail.