Nebenschilddrüsen-Zyste und Überfunktion

A 47-year-old man presented with a right-sided cervical lump and diagnosis of goiter. No swallowing disturbances or voice changes were recorded. Ultrasound and computed tomography scan revealed a cystic mass on the right thyroid (Fig 1). The results of the thyroid scintigram were normal. Laboratory tests were within a normal range except for parathyroidism (PTH): 130 pg/mL (normal, 9–65 pg/mL), serum calcium: 11.2 mg/dL (normal, 8.1–10.4 mg/dL), and serum phosphorus: 4.3 mg/dL (normal, 2.7–4.5 mg/dL). Fine-needle aspiration of the cyst revealed a clear fluid content with a PTH value of 3.450 pg/mL (normal, 9–65 pg/mL). Because of primary hyperparathyroidism diagnosis, the patient was operated on with the diagnosis of primary hyperparathyroidism and a large parathyroid cyst was removed (Fig 2). The remaining parathyroid glands and thyroid examination were normal. Intraoperative iPTH values returned to normal values by minute 10. Patient is in normal condition after 24-month follow-up.

Fig 1. Computed tomography scan shows a cystic mass on the neck displazing trachea

Fig 2. Operative field. Large cystic parathyroid cyst.

Comments
Parathyroid cysts are rare but significant lesions. They may occur in the cervical region and anywhere from the mandible to the mediastinum, including thymus.1 Traditionally they are classified as functional or nonfunctional. Overall, 33% are functional and account for 1% of all cases of hyperparathyroidism. Mediastinal cysts are more likely to be hyperfunctional, perhaps related to the fact that 75% of these cysts are larger than 5 cm in size. Seventy percent of the reported cases originate from the inferior gland.2 The origin of parathyroid cysts is not completely understood, but they may come from congenital cystic remnants of a branchial pouch, cystic degeneration of an adenoma, or enlargement of a microscopic cyst. Differential diagnosis include thyro-glossal duct cysts, branchial cleft cysts, cystic papillary cancer, and even esophageal duplication cysts.3
They are most often mistaken for more common lesions, such as thyroid cysts.1 There is not, currently, any radiographic method in differentiating parathyroid from thyroid cysts. Ultrasonography and computed tomography scan may provide information on the cystic nature of the lesion and topographic data. Radionuclide scan often demonstrates an area of decreased uptake, simulating a cold thyroid nodule, which thus makes likely the diagnosis of a thyroid nodule.4 Recent studies have demonstrated that parathyroid cyst are negative on sesta-2-methoxy isobutyl isonitrile (MIBI) scans. However, it is important to make the distinction from a thyroid nodule as the management may widely differ. Fine-needle aspiration is the most useful preoperative diagnostic technique revealing a high content of PTH.5 It can be also a treatment option, but most cases recur after 1 year. Intracystic alcohol injection has been also advocated. However, surgery is advised nowadays as the first option. In patients with clear symptoms of hyperparathyroidism, treatment does not vary much from parathyroid adenoma.

References
1 M.B. Ujiki, R. Nayar, C. Sturgeon and P. Angelos, Parathyroid cyst: often mistaken for a thyroid cyst, World J Surg 31 (2007), pp. 60–64.
2 S. Wani and Z. Hao, Atypical cystic adenoma of the parathyroid gland: case report and review of literature, Endocr Pract 11 (2005), pp. 389–393.
3 O. Cohen, J. Ilany and I. Shimon, Parathyroid cyst, Thyroid 14 (2004), pp. 325–326.
4 G. Ippolito, F.F. Palazzo, F. Sebag, M. Sierra, C. De Micco and J.F. Henry, A single-institution 25-year review of true parathyroid cysts, Langenbecks Arch Surg 391 (2006), pp. 13–18.
5 B. Shi, H. Guo and N. Tang, Treatment of parathyroid cyst with fine-needle aspiration, Ann Intern Med 131 (1999), pp. 797–798.

Miguel Echenique Elizondo, and José A. Amondarain

Surgery Volume 143, Issue 3, March 2008, Pages 447-448