Nonsecretory parathyroid carcinoma of the mediastinum. Light microscopic, immunocytochemical, and ultrastructural features of a case, and review of the literature.

Nonsecretory parathyroid carcinoma is rare, particularly in extracervical sites. The authors present a case of a 51-year-old man with a large mediastinal mass that was found on a chest x-ray. Light and electron microscopy and immunohistochemical analysis of the resected tumor disclosed findings consistent with parathyroid carcinoma. Clinical and laboratory evaluations failed to reveal evidence of hyperparathyroidism. The nonsecretory state of the tumor was further supported by immunoreactivity for parathormone in tissue sections and, at the same time, normal levels of this peptide in serum. Partial shrinkage of the mediastinal mass occurred after 11 months of combined chemotherapy, with subjective improvement. A literature review of both secretory and nonsecretory parathyroid carcinomas was undertaken, revealing similar clinical features with regard to mean age, age range, and sex incidence among both groups.