RECOGNIZING PARATHYROID CARCINOMA
U Srinivas Shankar, MK Rutter & D Ewins
Most cases of primary hyperparathyroidism are due to either parathyroid adenoma or hyperplasia. Parathyroid carcinoma is a rare cause of hyperparathyroidism, usually diagnosed post operatively .Prognosis is poor with a 5 year survival rate of 50-75%.
A 74 year old man presented with a 2 week history of weight loss, anorexia and constipation but no abdominal or bone pain. Past history included hypertension and gout and was not on drugs known to cause hypercalcaemia. Examination revealed a palpable mass in the lower pole of the right lobe of the thyroid gland. Serum calcium and serum PTH levels were elevated at 4.4 millimols per litre (NR 2.1-2.7) and 121 picomols per litre(NR 1.9-6.9)respectively .Renal function was impaired with a urea of 39 micromols per litre (NR 4.1 -10) and creatinine of 635 micromols per litre (NR 58-160).Serum alkaline phosphatase was elevated at 523 International Units per litre (NR 40-129).Plasma and urine protein electrophoresis, thyroid, liver function tests, serum phosphate, erythrocyte sedimentation rate and full blood count were normal. Chest X ray, renal ultrasound and
X ray of hands were normal. Following treatment with IV fluids and pamidronate, serum calcium level droppped to 2.54 millimols per litre and renal function improved. Ultrasound revealed a possible parathyroid mass compressing the lower pole of the right lobe of the thyroid gland.Surgery revealed a calcified mass (25x 23 x 15 millimeters) attached to the right lobe of thyroid, both of which were excised.Histological examination revealed features of a locally invasive parathyroid carcinoma. Post operatively serum calcium levels dropped further but hypocalcaemia was not a problem. He is scheduled for radiotherapy to the tumor bed.
This case highlights the need to consider the possibility of parathyroid carcinoma in every patient with primary hyperparathyroidism at the time of diagnosis and treatment , especially if there is a short history, palpable neck mass, high level of serum calcium and evidence of bone disease, as management and prognosis are different.