Water-clear cell Parathyroid adenoma: rare case report

ObjectiveWater-clear cell parathyroid adenoma (WCCA) is an extremely rare cause of primary hyperparathyroidism (PHPT). Our objective was to report a patient with a WCCA that was managed by our Department and to review the relevant literature in order to further our understanding of this rare entity.MethodsWe retrospectively reviewed the case notes, histopathological records and electronic notes of a patient with WCCA that was operated in our Endocrine Surgery department. Furthermore, we reviewed the relevant literature and report our findings using Medline database to search all the relevant medical data from 1946 till present without any language restriction using the keywords: water-clear-cell, water clear cell adenoma, water clear cell parathyroid adenoma.ResultsA 73-year-old female was referred to our Department by her GP with an incidental finding of hypercalcemia. The patient was completely asymptomatic in terms of PHPT clinical features. Her biochemistry results revealed hypercalcemia (3.04 mmol/L), high parathyroid hormone (279 ng/l), Vitamin D of 73 units, eGFR of 64 and an increase in 24-hour urinary calcium extraction (9.0 mmol/D). After the diagnosis of primary hyperparathyroidism (PHPT) was established we proceeded to localisation studies. Parathyroid Ultrasonography scan showed a right 30x11mm parathyroid lesion with enlarged lymph nodes. The 99mTc scan Sestamibi scan showed increased tracer accumulation at the right lower pole of the thyroid which failed to washout while SPECT CT confirmed a posterior right thyroid location. Bone densitometry showed osteoporosis at the patient’s left wrist and osteopenia in her femurs.In view of the extremely high calcium/PTH and the size of the lesion (3 cm) there was a concern for the possibility of parathyroid carcinoma and the patient had an oncologic operation (en bloc resection of right sterno-thyroid muscle, right thyroid lobe, right lower parathyroid, right level VI lymphadenectomy) in June 2018.Histology revealed the presence of a 3.1 cm WCAA of the right lower parathyroid gland, limited to the gland; resection margins were free of neoplasm. The neoplasm was well-circumscribed and non-encapsulated. It showed a trabecular-nested pattern with no solid/diffuse areas; the reticuline pattern was preserved with no fibre destruction, the elastic fibres were preserved with no abnormal deposition, and no fibrosis was identified on H&E or trichrome stained sections. A rim of compressed parathyroid parenchyma was noted at the periphery of the lesion and there was no extension or thyroid invasion. No lymphovascular or perineural invasion was seen. The tumour cells revealed broad water-clear cytoplasm, low nuclear pleomorphism, inconspicuous nucleolus, and In the immediate post-operative period the PTH dropped to 68 ng/l. The patient made an uneventful post-operative recovery and was discharged home on post-op day 1 with oral Alfacalcidol 1μgr BD, Calceos 1tab TDS and Sandocal tablets PRN. Oral calcium supplementation was discontinued on the 2nd week post-op and she has been normocalcemic up to her most recent follow-up. The case had been discussed in the endocrine multidisciplinary meeting and the consensus was that there should be ongoing monitoring of her calcium/PTH.On the literature review we performed, there are about 20 other cases reported as WCCA, all of which have been diagnosed on histopathology, 2 of the cases had been found to be intra-thyroidal and only one has been diagnosed as water-clear cell carcinoma. No change in the management or the frequency of the follow up had been suggested.ConclusionWCCA is a rare cause of PHPT, however the diagnosis with WCCA doesn’t change the management of the parathyroid adenoma in terms of operation and the follow up plans.