Parathyroid carcinosarcoma: a previously unreported entity.

Parathyroid carcinoma is a rare disease. The first report of parathyroid carcinoma with sarcomatous differentiation is presented. A parathyroid mass measuring 6 x 8 x 9 cm was surgically excised from the left side of the neck in a 54-year-old man who had mild hypercalcemia. Light microscopic examination of the mass showed carcinoma with areas of rhabdomyosarcoma and chondrosarcoma. Immunohistochemical studies confirmed the light microscopic impression. Resolution of hypercalcemia followed excision of the mass, but multiple pulmonary and adrenal masses subsequently developed and led to the patient's death despite aggressive trials of chemotherapy with doxorubicin, ifosfamide, and cisplatin. The sarcomatous elements of the mass excised from this patient are presumed to represent aberrant cellular differentiation previously described in uterine and other tissue but not in parathyroid glands. Sarcomatous differentiation itself appears to be a poor prognostic factor in parathyroid carcinoma.