An unusual mediastinal parathyroid carcinoma coproducing PTH and PTHrP: A case report

Parathyroid carcinoma (PTCA) is a rare disease, and ectopic PTCA is particularly rare. Parathyroid hormone-related protein (PTHrP) expression in PTCA has not been previously described in the relevant literature to the best of our knowledge. The present study reports a unique case with a mediastinal parathyroid carcinoma producing parathyroid hormone (PTH) and PTHrP. A 53-year-old man presented with hyperparathyroidism symptoms, including fatigue, chest pain, dizziness, muscular soreness, polyuria, night sweats and renal stones. However, neck ultrasound revealed no significantly abnormal thyroid or parathyroid nodules. Tc99m methoxyisobutylisonitrile (Tc99m-MIBI) scintigraphy scanning indicated an ectopic mediastinal parathyroid adenoma. Histopathological examination revealed PTCA, and the tumor tissue was coproducing PTH and PTHrP. The patient underwent successful surgical operation. Serum calcium and PTH levels remained within normal ranges, and there was no tumor recurrence observed at a 3-year follow-up appointment. Although rare, ectopic parathyroid glands may lead to malignant disease. Clinical symptoms, biochemical tests, ultrasound and Tc99m-MIBI scintigraphy scanning may assist with the diagnosis of this disease. Hypersecretion of PTHrP and PTH contributed collaboratively to the pathogenesis of hypercalcemia due to PTCA. Complete surgical resection with microscopically negative margins is the recommended treatment for PTCA and offers the best chance of a cure.