A patient suspected to have parathyroid carcinoma shows PTH >1500 pg/mL. What is the most useful intraoperative sign confirming carcinoma?
Answer: A
Explanation: Parathyroid carcinoma typically appears as a dense, fibrous, invasive tumor firmly adherent to the thyroid or strap muscles. Size alone is unreliable and lymphadenopathy is uncommon.
Teaching Points: Hallmark = local invasion/adherence.
• High PTH + severe hypercalcemia (often >14 mg/dL).
• En bloc resection is essential—no capsule violation.
A 46-year-old woman presents with recurrent nephrolithiasis and persistent hypercalcemia Labs: • Serum calcium: 12.1 mg/dL • PTH: 148 pg/mL • 24-hour urinary calcium: 60 mg/day (low) • Calcium/creatinine clearance ratio: 0.007 • Vitamin D: 32 ng/mL Neck ultrasound and sestamibi scans are negative. What is the most likely diagnosis?
Answer: B
Explanation: The key discriminator between FHH and primary hyperparathyroidism is urinary calcium excretion.
FHH presents with lifelong mild hypercalcemia, elevated or normal PTH, and markedly low urinary calcium. A calcium/creatinine clearance ratio <0.01 is diagnostic, as seen in this case (0.007).
Imaging is usually negative because FHH is not a surgical disease.
Primary HPT typically has higher urinary calcium levels.
Normocalcemic primary HPT is ruled out because the patient is hypercalcemic.
Tertiary HPT requires a background of chronic kidney disease.
Teaching Points: - CCCR <0.01 strongly suggests FHH, whereas >0.02 supports primary HPT.
- FHH is due to inactivating mutations in the CaSR gene and does not respond to surgery.
- Always check urinary calcium before planning parathyroidectomy.