Endocrine Abstracts

Less than 0.5% of parathyroid lesions are cysts out of which only 10–20% are endocrine active. Depending on their localisation, the most frequent symptom of a parathyroid cyst (PC) is neck mass (41.7%) with possible compressive symptoms. Women are more frequently affected and tend to have hormone-inactive PCs. Men tend to have endocrine-active PCs. The best diagnostic approach is still under debate as PCs are relatively rare.

Case report 1: A 68-year-old man was referred by the rheumatologists for primary hyperparathyroidism, which had been diagnosed as part of the extended investigations for CPPD arthritis. His history revealed recurrent kidney stones, chronic kidney disease and osteopenia (T-score minimal −2.0 S.D.) as possible associated secondary diseases. There were no local complaints or compression symptoms. The albumin-corrected calcium was 2.8 mmol/l and the PTH was 200 mmol/l. Ultrasonography showed a large cystic lesion (58 mm) caudal to the left lobe of the thyroid gland. The cyst fluid obtained by fine needle aspiration was hemorrhagic and contained high concentrations of PTH (305 000 ng/l). Intraoperatively, most of the cyst was retrosternal and could be removed intact. Histopathologically, the specimen weighed 28 g and could be clearly assigned to a cystic parathyroid adenoma.

Case report 2: A 74-year-old female patient was diagnosed with primary hyperparathyroidism as part of a search for secondary causes of osteoporosis (T-score minimal −4.5 S.D.). The serum calcium was 2.7 mmol/l, the PTH was 177 mmol/l. Sonography revealed a predominantly cystic mass with solid margins (max. 37 mm) in the area of the caudal right lobe of the thyroid gland, which could not be clearly differentiated from the thyroid gland. The choline PET/CT showed a choline-enriched lesion with strong margins dorsally adjacent to the right lobe of the thyroid gland. The findings could be surgically resected and histopathologically corresponded to a 5 g cystic parathyroid adenoma. A low normal PTH was measured in both patients on the 1st day postoperatively, the Calcium normalized in the following investigations.

Conclusion: The diagnosis of cystic parathyroid adenomas can be made by imaging or fine needle aspiration. To date, the diagnostic value of Tc-99m MIBI SPECT/CT in primary hyperparthyroidism caused by cystic parathyroid adenomas is unclear (no data for choline PET), and minimally invasive FNA appears to be very useful for the diagnosis and differentiation of other neck cysts due to the highly elevated PTH level in both endocrine active and inactive PCs, what is very characteristic.