Nuclear YAP1 accumulation was evident in a substantial proportion of parathyroid epithelial cells in normal parathyroid glands and parathyroid adenomas, while the accumulation of YAP1 in the cytosol was variably reduced in cells of parathyroid adenomas, which sometimes showed a more intense nuclear staining compared with cells in normal glands. This evidence concerns the gene YAP1 and parathyroid gland adenoma.