Water-clear cell adenoma: A rare form of hyperparathyroidism

Primary hyperparathyroidism is a common endocrine disorder, with an incidence of 21.6 per 100,000 person-years. Asymptomatic elevated serum calcium levels on routine biochemical investigations accounts for 80% of newly diagnosed primary hyperparathyroidism. Solitary adenoma is the commonest cause of primary hyperparathyroidism and can be treated by excision of a single gland.

We present a case of primary hyperparathyroidism in a 74-year-old female was referred to our surgery endocrine outpatients for assessment of a persistently elevated calcium level, lower abdominal pain and constipation. Biochemical analysis revealed corrected serum calcium of 3.13mmol/L (reference range 2.17-2.51mmol/L) and an intact parathyroid hormone level (iPTH) of 488.9ng/L (reference range 15-65ng/L). Sestamibi scan localised a persistent increased area of activity inferior to the lower pole of the left lobe of thyroid gland.

The patient underwent a minimally invasive parathyroidectomy using a 3cm incision with intra-op radionucliotide localisation. At surgery a single large parathyroid gland measuring 5.5cm was excised without complication. Grossly the parathyroid gland was an encapsulated tan mass measuring 5.5cm×2.5cm×2cm and weight 13g and histological assessment revealed a water-clear cell (WCC) adenoma. She made an uneventful post op recovery with normalisation of her serum calcium.

WCC adenomas have a "low endocrinological activity" in which serum calcium levels do not elevate until the adenoma has reached considerable size. Our case supports this hypothesis and aids to the understanding of these rare tumours.