Synchronous water-clear cell double parathyroid adenomas - A hitherto uncharacterized entity?

Water-clear cell hyperplasia is a rare but well-documented cause of primary hyperparathyroidism. Parathyroid adenomas of the water-clear cell type are exceptionally rare, and only 2 cases have been reported. We describe a pat ient with synchronous water-clear cell double parathyroid adenomas, an enti ty that has not previously been reported. In our case, the enlarged superio r parathyroid glands were completely replaced by water-clear cells, with on ly a minute rim of extracapsular, histologically unremarkable parathyroid t issue. The inferior parathyroid glands were grossly unremarkable, and incis ional biopsy specimens were histologically normal (no foci of water-clear c ells were identified). The findings in this case are most consistent with t he diagnosis of double adenomas of the water-clear cell type. We acknowledg e that despite molecular proof of monoclonality of the 2 lesions, it is not possible to entirely exclude the possibility that this unusual case could be due to asymmetric hyperplasia.