Spontaneous remission of hypercalcemia in a functioning parathyroid cyst.

We treated a patient with a hyperfunctioning parathyroid cyst detected incidentally and which disappeared spontaneously. High levels of plasma PTH disappeared after removal of the cystic lesion of the parathyroid gland. Histologically, a secondary pseudocyst resulting from a cystic degeneration of an adenoma was observed. Minor hemorrhage of an unknown cause, within the adenoma, led to the large cystic lesion of the parathyroid gland.