Clinical Information: This 74 year old female presented with primary hyperparathyroidism. She underwent a right parathyroidectomy.
What is your diagnosis?
Discussion and answer
Diagnosis: Macroscopically, a lobulated encapsulated mass measuring 2.7 cm in greatest dimension was identified.
Microscopically, there is a multinodular encapsulated lesion composed primarily of chief cells with a network of small capillaries dispersed throughout the lesion. The tumour nuclei are uniform and bland. No mitoses are identified. Normal appearing parathyroid tissue is seen at the periphery.
The diagnosis is parathyroid adenoma. 75-80% of primary hyperparathyroidism is caused by a solitary adenoma. These lesions are encapsulated, composed of chief cells and have a delicate network of capillaries throughout. Typically, a rim of residual parathyroid tissue is seen.
Other causes for primary hyperparathyroidism include parathyroid hyperplasia (15% cases) and parathyroid carcinoma (1-2% cases), which must be excluded. Parathyroid hyperplasia is suggested when all four glands are enlarged. Other features include diffuse sheets of chief cells, no rim of normal tissue and possible mitotic figures. A diagnosis of parathyroid carcinoma is suggested with a trabecular arrangement of tumour cells divided by thick fibrous bands, capsular and vascular invasion and mitotic figures.