Ectopic atypical parathyroid lipoadenoma: a rare cause of severe primary hyperparathyroidism.

Parathyroid lipoadenomas are a rare and benign variant of parathyroid adenomas that are defined morphologically by an abundance of fat cells. They may be functional with secretion of parathyroid hormone or nonfunctional. We present a case of a parathyroid lipoadenoma in a patient presenting with clinical manifestations of severe primary hyperparathyroidism. Unusual features in this case included the ectopic location of the lipoadenoma in the mediastinum, the significant size of 6.6 × 3.4 cm, and weight of 30.1 g. In addition to the large size of this generally benign type of parathyroid neoplasm, histologic findings included focal band-forming fibrosis compatible with the diagnosis of an atypical parathyroid adenoma. In conclusion, this case illustrates a difficult case of an ectopic functioning parathyroid lipoadenoma with chronic sequelae due to severe hyperparathyroidism.