Dedifferentiated liposarcoma and 1,25 dihydroxyvitamin D-induced paraneoplastic hypercalcaemia.

Hypercalcaemia of malignancy (HM) can result from excess parathyroid hormone-related peptide (PTHrP), osteolysis from bone metastasis or overproduction of 1,25 dihydroxyvitamin D (1,25[OH]2D) by the enzyme 1-α hydroxylase. HM among sarcomas is rare, with the most common mechanism being overproduction of PTHrP. There are only three published cases of sarcoma-related HM caused by overproduction of 1,25[OH]2D. We herein report a patient who presented with abdominal pain and generalised weakness and was diagnosed with a large multifocal retroperitoneal dedifferentiated liposarcoma. His bloodwork showed severe hypercalcaemia and extensive workup revealed 1,25[OH]2D-related HM. He was treated with intravenous fluids, bisphosphonates, glucocorticoids and cytotoxic chemotherapy with improvement in his pain and normalisation of his calcium levels. We describe the unique features of his case and review existing reports of 1,25[OH]2D and PTHrP-associated HM in sarcomas.