CONFRONTING THE ELUSIVE GIANT

A RARE CASE OF GIANT CYSTIC PARATHYROID ADENOMA

Abstract

INTRODUCTION/BACKGROUND

Giant cystic parathyroid adenomas are an uncommon cause of primary hyperparathyroidism and may result in severe hypercalcemia. Due to their cystic nature, they can evade detection by conventional imaging such as Sestamibi scans, posing diagnostic challenges. We report a case of a 60-year-old female with a giant cystic parathyroid adenoma, where conventional imaging failed to identify the lesion.

CASE

A 60-year-old female with hypertension and stage 4 chronic kidney disease presented with a three-month history of diffuse goitre and asymptomatic hypercalcemia (corrected calcium 3.11–3.77 mmol/L). Investigations showed elevated iPTH (160.3 pmol/L), low phosphate (0.75 mmol/L), low vitamin D (33.25 nmol/L), with normal thyroid function. Neck ultrasound detected a benign thyroid nodule (TIRADS 1), but no parathyroid lesion. A Sestamibi scan was negative for hyperfunctioning or ectopic parathyroid tissue and showed only cystic changes in the thyroid.

Due to persistent hypercalcemia, CT imaging was performed and revealed a large cystic mass on the left neck (4.2 × 6.2 × 10.8 cm), suggestive of a cystic parathyroid adenoma. The patient had osteopenia and required multiple pamidronate infusions. She underwent a left parathyroidectomy, during which a large cystic parathyroid tumor was removed. Postoperative calcium levels normalized, and histopathology confirmed cystic parathyroid adenoma.

Sestamibi scans may not detect cystic parathyroid adenomas due to poor radiotracer uptake in cystic tissue. CT imaging played a key role in identifying the lesion in this case. Awareness of false-negative imaging results is essential to avoid delayed treatment and complications.

CONCLUSION

Negative Sestamibi scans do not exclude parathyroid pathologies, particularly in the presence of cystic adenomas. Clinicians should maintain a high index of suspicion and use complementary imaging modalities to avoid delays in treatment.