GIANT PARATYROID ADENOMA VERSUS PARATHYROID CARCINOMA

TWO CASE REPORTS AND LITERATURE REVIEW

Abstract

INTRODUCTION
Primary hyperparathyroidism is not an uncommon disorder in our region. Eighty to 90% of cases of primary hyperparathyroidism are due to solitary parathyroid adenoma, with only 1% due to parathyroid carcinoma. Giant parathyroid adenoma is defined by a tumor weight or >3.5 g. Parathyroid carcinoma should also be considered in patients with giant adenoma.

METHODOLOGY
Case 1 is a 78-year-old Chinese lady, with underlying hypertension and breast cancer in remission. She presented with dizziness and mild hypercalcemic symptoms. Serum calcium level was 3.61 mmol/L, with intact parathyroid hormone (iPTH) level of 88.2 pmol/L. Neck ultrasonography showed a large right inferior pole parathyroid adenoma, measuring 5.5 cm x 3.0 cm x 6.6 cm. Intraoperatively, a large parathyroid gland weighing 38 g was resected and reported as parathyroid carcinoma with soft tissue and vascular invasion. She developed mild hypocalcemia postoperatively. Case 2 is a 19-year-old Malay lady who presented with bilateral pathologic fractures of the hip and severe hypercalcemic symptoms. Elevated serum calcium (4.18 mmol/L) and iPTH (186 pmol/L) levels were noted. Neck ultrasonography revealed a left parathyroid adenoma measuring 2.2. cm x 1.5 cm x 3.5 cm. Intraoperatively, a 7 g
parathyroid gland was resected, which was subsequently reported as parathyroid adenoma. Postoperatively, she developed hungry bone syndrome with prolonged hospital stay (16 days). Repeated iPTH and serum calcium done 6 weeks postoperatively were normal for both patients.

RESULTS
Giant parathyroid adenoma is a rare entity with distinct manifestations, but may also be asymptomatic. Patients have higher preoperative serum calcium and iPTH levels, with significant occurrence of symptomatic postoperative hypocalcemia, as presented by Case 2. On the other hand, parathyroid carcinoma should also be suspected in a patient with an unusually large tumor, higher serum calcium (>3.5 mmol/L) and iPTH (10 times the normal upper limit) levels, as in Cases 1 and 2. Histopathologic examinations will confirm parathyroid carcinoma.

CONCLUSION
It is important to suspect both cases parathyroid carcinoma or giant adenoma as this will determine the surgical and further management.