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Radiology Quiz Case 1: Diagnosis

Radiology Quiz Case 1: Diagnosis Diagnosis: Parathyroid cyst (PC) Parathyroid cysts are rare, often asymptomatic lesions that are frequently discovered incidentally. As a result, they are very low on, or absent from, the list of differential diagnoses of a neck mass. In cases of incidental discovery of the lesion and without associated signs or symptoms of hyperparathyroidism, PCs present a clinical diagnostic problem. Diagnosis is often made intraoperatively or postoperatively in these cases, either by frozen section of the mass or by postresection pathologic analysis. This delay is undesirable given the wide differential diagnosis and range of treatments for neck masses. Radiologic evaluation is essential for a preoperative diagnosis. In this case, fine-needle aspiration of the cyst contents was performed under ultrasonographic guidance after computed tomograms and magnetic resonance images revealed a cystic lesion in the lower part of the left side of our patient's neck. Ultrasonograms showed a unilocular cystic lesion near the inferior pole of the left thyroid lobe. Fine-needle aspiration produced 10.5 mL of clear fluid. Microscopic examination of the fluid revealed proteinaceous material with a few crystalline particles and tissue macrophages. Based on the needle biopsy findings, the mass was thought to be a PC, a small cystic hygroma, or a cystic thyroid nodule. The aspirate was submitted for parathyroid hormone (PTH) assay, and the results showed that the level of PTH was highly elevated (5590 pg/mL [to convert to nanograms per liter, multiply by 1]), confirming the diagnosis of PC. The patient was then taken to the operating room for excision of the left lower parathyroid gland and associated cyst. The surgical specimen was 2.5 × 2.0 × 1.1 cm and weighed 6.4 g. Representative histopathologic sections are shown in Figure 4. Figure 4. View LargeDownload Parathyroid cysts typically occur in the fourth and fifth decades of life and more often in women than men, with a 3:2 ratio.1They can be found anywhere between the jaw and the mediastinum but are most commonly located on the inferior parathyroid glands, where they demonstrate a left-sided predominance.1,2Mediastinal PCs have been reported in up to 30% of cases and generally involve the anterior mediastinum in association with normal thymic tissue.3 The pathogenesis of PCs is unknown, but several theories have been proposed. First, the cyst may arise from embryological remnants of the third or fourth branchial clefts. Secretion of colloid material containing PTH into a cell-lined cavity may result in the formation of a cyst over time.1,4Second, PCs may represent a degenerated parathyroid adenoma.1After formation of a secretory adenoma, involution of a portion of the lesion may result in the formation of a cavity containing proteinaceous material and PTH. Finally, a macroscopic PC may be formed by the coalescence of many microcysts. This theory is attractive given the high prevalence of microcysts in normal individuals at autopsy. Although macroscopic PCs are rare, microcysts are common in the aging parathyroid gland, and the incidence of parathyroid cysts at autopsy has been reported to be as high as 40% to 50%.1,4,5 Parathyroid cysts rarely manifest systemic disease, and fewer than 10% are associated with hyperparathyroidism and subsequent hypercalcemia.5Cyst fluid often contains elevated levels of PTH, although serum PTH levels are within normal limits in most cases. In 1 review of 37 patients with PCs, the intact PTH level in the cystic fluid ranged from 81 to 2000 pg/mL (mean, 552 pg/mL), although all of these cysts were nonfunctional as demonstrated by normal serum calcium, phosphorus, and intact PTH levels.6In functioning PCs, PTH levels in the cystic fluid can reach several million picograms per milliliter.7Functional PCs have been associated with elevated serum PTH levels and malignant hypercalcemia, producing kidney stones, weakness, confusion, and even brown tumors (osteitis fibrosa cystica) of the maxilla and tibia.3,8 Parathyroid cysts commonly measure between 3 and 5 cm in diameter; however, masses as large as 12 cm have been reported. Larger cysts can impinge on local structures and may produce symptoms of dyspnea, dysphagia, chest pain, or hoarseness. Thrombosis and compression of the left innominant vein have been reported.3Diagnosis can be made on histopathologic examination of the excised lesion, which may demonstrate a characteristic thin, membranous lining of cuboidal or columnar epithelium with parathyroid tissue within the cyst wall.1 Definitive treatment of a PC is surgical resection of the cyst and associated parathyroid tissue. For cysts occurring in the neck, the approach and removal of the cyst are essentially the same as those of a standard selective parathyroidectomy. Mediastinal lesions, however, may require the assistance of a thoracic surgeon. Some authors have suggested that aspiration alone is adequate treatment of a nonfunctional cyst6,9; however, 1 study found that 3 of 4 patients who were treated with aspiration alone required multiple aspirations.10Finally, injection of sclerosing agents such as tetracycline has been suggested, particularly for recurrent cysts that had previously been treated with aspiration alone. This procedure, however, carries the risk of misdirected injection of the sclerosing agent and subsequent injury to normal thyroid tissue or the recurrent laryngeal nerve. The sclerosed cyst may undergo fibrosis, with a poor cosmetic result.1 In conclusion, PCs are a rare cause of neck masses. Cystic lesions in the neck and mediastinum should be subjected to fine-needle aspiration and determination of PTH level. Although PCs are rarely functional, treatment is indicated to arrest growth of the lesion, to prevent potential mass effect complications such as airway compromise, and to preserve the normal contour of the neck. We believe that surgical resection is the best treatment for PCs. Return to Quiz Case 1. References 1. Fortson JKPatel VGHenderson VJ Parathyroid cysts: a case report and review of the literature. Laryngoscope 2001;111 (10) 1726- 1728PubMedGoogle ScholarCrossref 2. Jha BCNagarkar NMKochhar SMohan HDass A Parathyroid cyst: a rare cause of an anterior neck mass. J Laryngol Otol 1999;113 (1) 73- 75PubMedGoogle ScholarCrossref 3. Shields TWImmerman SC Mediastinal parathyroid cysts revisited. Ann Thorac Surg 1999;67 (2) 581- 590PubMedGoogle ScholarCrossref 4. Katz ADDunkleman D Needle aspiration of nonfunctioning parathyroid cysts. Arch Surg 1984;119 (3) 307- 308PubMedGoogle ScholarCrossref 5. Lydiatt DDByers RMKhouri KGWhitworth PWSellin RV Functional parathyroid cyst and hypocalciuric hypercalcemia. Ear Nose Throat J 1993;72 (2) 142- 144PubMedGoogle Scholar 6. Ippolito GPalazzo FFSebag FSierra MDe Micco CHenry JF A single-institution 25-year review of true parathyroid cysts. Langenbecks Arch Surg 2006;391 (1) 13- 18PubMedGoogle ScholarCrossref 7. Spitz AF Management of a functioning mediastinal parathyroid cyst. J Clin Endocrinol Metab 1995;80 (10) 2866- 2868PubMedGoogle Scholar 8. Oh AMojica PSullivan M et al. Malignant hypercalcemia associated with a parathyroid macrocyst and the early genesis of a giant cell tumor. Am J Otolaryngol 2006;27 (1) 54- 57PubMedGoogle ScholarCrossref 9. Kodama TObara TFujimoto YIto YYashiro THirayama A Eleven cases of nonfunctioning parathyroid cyst—significance of needle aspiration in diagnosis and management. Endocrinol Jpn 1987;34 (5) 769- 777PubMedGoogle ScholarCrossref 10. Ujiki MBNayar RSturgeon CAngelos P Parathyroid cyst: often mistaken for a thyroid cyst. World J Surg 2007;31 (1) 60- 64PubMedGoogle ScholarCrossref http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Otolaryngology - Head & Neck Surgery American Medical Association

Radiology Quiz Case 1: Diagnosis

Archives of Otolaryngology - Head & Neck Surgery , Volume 136 (9) – Sep 20, 2010

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References (10)

Publisher
American Medical Association
Copyright
Copyright © 2010 American Medical Association. All Rights Reserved.
ISSN
0886-4470
eISSN
1538-361X
DOI
10.1001/archoto.2010.140-b
Publisher site
See Article on Publisher Site

Abstract

Diagnosis: Parathyroid cyst (PC) Parathyroid cysts are rare, often asymptomatic lesions that are frequently discovered incidentally. As a result, they are very low on, or absent from, the list of differential diagnoses of a neck mass. In cases of incidental discovery of the lesion and without associated signs or symptoms of hyperparathyroidism, PCs present a clinical diagnostic problem. Diagnosis is often made intraoperatively or postoperatively in these cases, either by frozen section of the mass or by postresection pathologic analysis. This delay is undesirable given the wide differential diagnosis and range of treatments for neck masses. Radiologic evaluation is essential for a preoperative diagnosis. In this case, fine-needle aspiration of the cyst contents was performed under ultrasonographic guidance after computed tomograms and magnetic resonance images revealed a cystic lesion in the lower part of the left side of our patient's neck. Ultrasonograms showed a unilocular cystic lesion near the inferior pole of the left thyroid lobe. Fine-needle aspiration produced 10.5 mL of clear fluid. Microscopic examination of the fluid revealed proteinaceous material with a few crystalline particles and tissue macrophages. Based on the needle biopsy findings, the mass was thought to be a PC, a small cystic hygroma, or a cystic thyroid nodule. The aspirate was submitted for parathyroid hormone (PTH) assay, and the results showed that the level of PTH was highly elevated (5590 pg/mL [to convert to nanograms per liter, multiply by 1]), confirming the diagnosis of PC. The patient was then taken to the operating room for excision of the left lower parathyroid gland and associated cyst. The surgical specimen was 2.5 × 2.0 × 1.1 cm and weighed 6.4 g. Representative histopathologic sections are shown in Figure 4. Figure 4. View LargeDownload Parathyroid cysts typically occur in the fourth and fifth decades of life and more often in women than men, with a 3:2 ratio.1They can be found anywhere between the jaw and the mediastinum but are most commonly located on the inferior parathyroid glands, where they demonstrate a left-sided predominance.1,2Mediastinal PCs have been reported in up to 30% of cases and generally involve the anterior mediastinum in association with normal thymic tissue.3 The pathogenesis of PCs is unknown, but several theories have been proposed. First, the cyst may arise from embryological remnants of the third or fourth branchial clefts. Secretion of colloid material containing PTH into a cell-lined cavity may result in the formation of a cyst over time.1,4Second, PCs may represent a degenerated parathyroid adenoma.1After formation of a secretory adenoma, involution of a portion of the lesion may result in the formation of a cavity containing proteinaceous material and PTH. Finally, a macroscopic PC may be formed by the coalescence of many microcysts. This theory is attractive given the high prevalence of microcysts in normal individuals at autopsy. Although macroscopic PCs are rare, microcysts are common in the aging parathyroid gland, and the incidence of parathyroid cysts at autopsy has been reported to be as high as 40% to 50%.1,4,5 Parathyroid cysts rarely manifest systemic disease, and fewer than 10% are associated with hyperparathyroidism and subsequent hypercalcemia.5Cyst fluid often contains elevated levels of PTH, although serum PTH levels are within normal limits in most cases. In 1 review of 37 patients with PCs, the intact PTH level in the cystic fluid ranged from 81 to 2000 pg/mL (mean, 552 pg/mL), although all of these cysts were nonfunctional as demonstrated by normal serum calcium, phosphorus, and intact PTH levels.6In functioning PCs, PTH levels in the cystic fluid can reach several million picograms per milliliter.7Functional PCs have been associated with elevated serum PTH levels and malignant hypercalcemia, producing kidney stones, weakness, confusion, and even brown tumors (osteitis fibrosa cystica) of the maxilla and tibia.3,8 Parathyroid cysts commonly measure between 3 and 5 cm in diameter; however, masses as large as 12 cm have been reported. Larger cysts can impinge on local structures and may produce symptoms of dyspnea, dysphagia, chest pain, or hoarseness. Thrombosis and compression of the left innominant vein have been reported.3Diagnosis can be made on histopathologic examination of the excised lesion, which may demonstrate a characteristic thin, membranous lining of cuboidal or columnar epithelium with parathyroid tissue within the cyst wall.1 Definitive treatment of a PC is surgical resection of the cyst and associated parathyroid tissue. For cysts occurring in the neck, the approach and removal of the cyst are essentially the same as those of a standard selective parathyroidectomy. Mediastinal lesions, however, may require the assistance of a thoracic surgeon. Some authors have suggested that aspiration alone is adequate treatment of a nonfunctional cyst6,9; however, 1 study found that 3 of 4 patients who were treated with aspiration alone required multiple aspirations.10Finally, injection of sclerosing agents such as tetracycline has been suggested, particularly for recurrent cysts that had previously been treated with aspiration alone. This procedure, however, carries the risk of misdirected injection of the sclerosing agent and subsequent injury to normal thyroid tissue or the recurrent laryngeal nerve. The sclerosed cyst may undergo fibrosis, with a poor cosmetic result.1 In conclusion, PCs are a rare cause of neck masses. Cystic lesions in the neck and mediastinum should be subjected to fine-needle aspiration and determination of PTH level. Although PCs are rarely functional, treatment is indicated to arrest growth of the lesion, to prevent potential mass effect complications such as airway compromise, and to preserve the normal contour of the neck. We believe that surgical resection is the best treatment for PCs. Return to Quiz Case 1. References 1. Fortson JKPatel VGHenderson VJ Parathyroid cysts: a case report and review of the literature. Laryngoscope 2001;111 (10) 1726- 1728PubMedGoogle ScholarCrossref 2. Jha BCNagarkar NMKochhar SMohan HDass A Parathyroid cyst: a rare cause of an anterior neck mass. J Laryngol Otol 1999;113 (1) 73- 75PubMedGoogle ScholarCrossref 3. Shields TWImmerman SC Mediastinal parathyroid cysts revisited. Ann Thorac Surg 1999;67 (2) 581- 590PubMedGoogle ScholarCrossref 4. Katz ADDunkleman D Needle aspiration of nonfunctioning parathyroid cysts. Arch Surg 1984;119 (3) 307- 308PubMedGoogle ScholarCrossref 5. Lydiatt DDByers RMKhouri KGWhitworth PWSellin RV Functional parathyroid cyst and hypocalciuric hypercalcemia. Ear Nose Throat J 1993;72 (2) 142- 144PubMedGoogle Scholar 6. Ippolito GPalazzo FFSebag FSierra MDe Micco CHenry JF A single-institution 25-year review of true parathyroid cysts. Langenbecks Arch Surg 2006;391 (1) 13- 18PubMedGoogle ScholarCrossref 7. Spitz AF Management of a functioning mediastinal parathyroid cyst. J Clin Endocrinol Metab 1995;80 (10) 2866- 2868PubMedGoogle Scholar 8. Oh AMojica PSullivan M et al. Malignant hypercalcemia associated with a parathyroid macrocyst and the early genesis of a giant cell tumor. Am J Otolaryngol 2006;27 (1) 54- 57PubMedGoogle ScholarCrossref 9. Kodama TObara TFujimoto YIto YYashiro THirayama A Eleven cases of nonfunctioning parathyroid cyst—significance of needle aspiration in diagnosis and management. Endocrinol Jpn 1987;34 (5) 769- 777PubMedGoogle ScholarCrossref 10. Ujiki MBNayar RSturgeon CAngelos P Parathyroid cyst: often mistaken for a thyroid cyst. World J Surg 2007;31 (1) 60- 64PubMedGoogle ScholarCrossref

Journal

Archives of Otolaryngology - Head & Neck SurgeryAmerican Medical Association

Published: Sep 20, 2010

Keywords: cysts,radiology specialty,parathyroid

There are no references for this article.