CCND1 and tumor of parathyroid gland: Loss of retinoblastoma protein expression and increased cyclin D1 expression, which are found in >95% and 90%30 of human PCs, respectively, were not found to occur in the parathyroid tumours from Cdc73+/−, Cdc73+/L/PTH-Cre and Cdc73L/L/PTH-Cre mice (data not shown).