ATYPICAL PARATHYROID TUMOR

CHALLENGES OF DIAGNOSIS AND MANAGEMENT

Abstract

INTRODUCTION/BACKGROUND
Differentiating between benign and malignant parathyroid nodules is a clinical and pathological challenge. Unlike other tumours, parathyroid carcinoma lacks definitive preoperative biomarkers. The diagnosis is frequently made retrospectively based on surgical pathology.

CASE
A 55-year-old female came to our hospital with progressive bilateral weakness of lower extremities 6 months ago, resulting in partial immobilization, bone pain, and contracture of lower extremity. Laboratory results showed high serum calcium (13.9 mg/dL) and intact PTH (2,729 pg/mL). Neck ultrasound revealed a left parathyroid nodule mass. The MIBI scan showed a negative result. Bone X-ray of vertebra and extremities showed multiple lytic lesions and osteopenia. She was treated with zoledronic acid and scheduled for subtotal parathyroidectomy. After parathyroid resection, iPTH levels decreased significantly. However, she had low calcium levels, indicating hungry bone syndrome, and we managed with oral and IV calcium to restore normal calcium levels.

The histopathology of parathyroid nodules showed neoplasms of parathyroid origin that show atypical histologic features but without unequivocal capsular, vascular, or perineural invasion. During hospitalizations, she had a pathological closed fracture of the right tibia. The orthopedic surgeon placed an internal fixation in the right tibia and did a bone biopsy, which showed no malignant cells. We diagnosed her as having an atypical parathyroid tumor (APT) with metabolic bone disease and gave her IV Denosumab. After routine physiotherapy, she could mobilize around the bed and was eventually discharged with normal calcium levels. We planned for serum calcium and PTH evaluation 3–6 months after surgery.

CONCLUSION
APT is a distinct and enigmatic entity between benign adenoma and malignant carcinoma of parathyroid tumour. These tumours exhibit some worrisome histologic features of malignancy but lack definitive evidence of parathyroid carcinoma. APT is usually indolent. The prognosis is generally favourable if the tumour is completely resected and closely monitored.