[Primary hyperparathyroidism as a cause of hypercalcemia in a patient with breast cancer]

Hypercalcemia associated with breast cancer arises either from metastatic bone disease or from paraneoplastic secretion of parathyroid hormone-related peptide. We report a female 69-year-old patient with invasive intraductal breast cancer and hypercalcemia (3,4 mmol/l) referred to endocrinologist. Standard care in oncology was refused and with respect to the presence of estrogenic receptors the patient accepted only antiestrogenic treatment. Bone scan revealed no skeletal metastasis. Entry laboratory exam confirmed hypercalcemia, hypophosphatemia and significantly elevated parathyroid hormone (793 ng/l). The patient complained of bone pain and dyspepsia. Neck ultrasound showed a multinodular goiter with particularly enlarged left lobe. Parathyroid gland scintigraphy revealed a possible parathyroid adenoma behind the lower pole of the left thyroid lobe. The patient underwent thyroidectomy with an excision of the parathyroid mass. Microscopic examination identified a benign adenomatous goitre and benign parathyroid adenoma. Postoperatively, both serum calcium and parathyroid hormone normalized. Replacement of calcium and vitamin D were initiated both with bisphosphonate with regard to newly diagnosed osteoporosis. This case demonstrates a patient with breast cancer and hypercalcemia unrelated to the malignant disease. Primary hyperparathyroidism should be considered as a possible cause of hypercalcemia in breast cancer patients in the setting of negative bone scan, elevated parathyroid hormone and mildly deteriorated bone mineral density.