Cyclin D1 or CCND1 was initially designated PRAD1 or BCL1. PRAD1 was found to be clonally rearranged on chromosome 11q13 with PTH (parathyroid hormone) in parathyroid adenomas, resulting in overexpression of cyclin D1 [3–5]. The gene discussed is PTH; the disease is parathyroid gland adenoma.