Benign Neoplasms of the Parathyroid Gland

■

Parathyroid Adenoma

A parathyroid gland adenoma is an encapsulated benign neoplasm of the parathyroid parenchymal cells (either chief or oncocytic cells). Parathyroid disease is separated into primary, secondary, or tertiary, based on whether the parathyroid gland is primarily the source of the disease or if the gland is reacting to exogenous stimulation, such as renal disease ( Chapter 26 ). This distinction is sometimes quite difficult on histology alone and even more so if only a single gland is sampled. Intraoperative selective venous parathyroid hormone (PTH) assay is a clinical parameter which may assist with the distinction. Isolated cases of adenoma are associated with exposure to ionizing radiation (fourfold increase in Hiroshima-exposed patients), but the majority have no specific etiology. A small subset of cases present as part of the hyperparathyroidism–jaw tumor (HPT-JT) syndrome, an autosomal dominant disorder ( CDC73 gene at 1q25-q31) characterized by parathyroid adenoma or carcinoma, various fibro-osseous lesions of jaw (ossifying fibroma), and renal cysts or tumors. Up to 80% of the patients will have HPT.