Ectopic Pleural Parathyroid Adenoma Causing Recurrent Primary Hyperparathyroidism.

Ectopic parathyroid glands can cause primary hyperparathyroidism (PHPT) in up to 16% of cases. These can lead to recurrent/persistent PHPT, and multiple cases have been described in the literature. We present a case of a pleural parathyroid adenoma leading to persistent PHPT. The ectopic location of the parathyroid glands is a result of their migration during development and is next to tissues they share a common embryologic origin with. The pleural location of the parathyroid adenoma in our patient was highly unusual, as the pleura have an embryologically distinct origin from the parathyroids. This was likely the result of incomplete removal of a previous mediastinal adenoma or seeding of abnormal cells in the surrounding tissue due to capsular breach (parathyromatosis). These can lead to recurrent/persistent PHPT. Parathyromatosis can lead to the presence of adenomas in highly unusual locations, making diagnosis and treatment difficult. To our knowledge, this is the first reported case in the literature of pleural adenoma causing persistent PHPT.