Endocrine Abstracts

Introduction: Atypical parathyroid adenoma (APA) is rarely encountered cause of primary hyperparathyroidism (PHPT). No definite criteria are considered to distinguish preoperatively APA from parathyroid typical adenoma or carcinoma.

The aim

To describe the clinical course of a patient with an atypical parathyroid adenoma with severe hypercalcemia and multiple fragility fractures.

Case presentation: A 61-year-old woman was evaluated for multiple fractures, skeletal deformities, pain in the large joints and bones, tachycardia, oppressive chest pain. She had severe hypercalcemia (calcium level 14.7 mg/dl), hypophosphatemia (serum phosphate 2.1 mg/dl) with an elevated intact parathyroid hormone level of 1871 pg/ml. Ultrasonography revealed a large structure (4.7 cm) of the right parathyroid gland. 99mTc-sestamibi SPECT/CT showed the lesion 43×34×40 mm behind the middle and lower third of the left thyroid lobe. Renal function was impaired, GFR 46 ml/min/1.73 m². Whole-body Tc-99m bone scan demonstrated multiple skeletal changes accepted as parathyroid osteodystrophy. As a result of the determination of severe hypercalcemia, heart rhythm disturbances (permanent form of atrial fibrillation), a high risk of hypercalcemic crisis, intravenous hydration was started with no significant effect. Patient received denosumab 60 mg s.c. She underwent a surgical resection of parathyroid adenoma and intra-operative PTH levels fell to 20.9 pg/ml. In the postoperative period serum calcium was decreased to 8.9 mg/dl. On pathological examination, the tumor consisted mainly of chief cells. Capsule invasion, peripherical vascular and perineural invasion of the adjacent tissue, high mitotic activity or large bands of fibrosis were not observed. Ki67 immunostaining was generally positive in about 3% of the tumor. Tumor vessel invasion was detected in the central node part. These changes corroborated the diagnosis of atypical parathyroid adenoma.

Conclusion: APA are rare and have been a challenge for diagnosis. They have some features of carcinoma but lack the indisputable evidence of malignant disease like invasion or metastases. They have unpredictable clinical course, long-term follow up is prudent to assess for local recurrence and metastatic disorder to distinguish between benign and malignant parathyroid disease.