A very rare, slow-growing, clinically serious endocrine tumor that generally develops in mid-adulthood. PRTC presents as a palpable painless mass in the neck and causes severe hypercalcemia and related symptoms, non-specific gastrointestinal manifestations, as well as renal and bone complications related to primary hyperparathyroidism (nephrolithiasis, impaired renal function, osteoporosis, bone pain, and pathologic fractures, etc.). Some PRTCs are however non-functioning tumors.