the differential diagnosis of cystic cervical masses includes thyroid cyst , thymic cyst , thyroglossal duct cyst , branchial cleft cyst , bronchogenic cyst , lymphangioma and parathyroid cyst ( pc ) ( 1 ) . since then , approximately 300 cases have been reported in the world literature ( 2 ) . they may be functional or nonfunctional , depending on the presence or absence of the hyperparathyroidism and treatment options vary for both presentations . we herein report a patient diagnosed as pc and treated conservatively , while reviewing of the literature . a 56-year - old woman presented with a left - sided cervical lump with three months history . no dyspnea , swallowing disturbance or voice changes were recorded . at the physical examination , a soft , roundish ultrasound of the neck revealed a cystic mass in the left lower pole of the thyroid 21 cm in size and the radiologist suspected the diagnosis of thyroid nodule or parathyroid mass ( figure 1 ) . ultrasonographic view of the neck revealed a cystic mass in the left pole of the thyroid thyroid function tests including triiodothyronine , thyroxin and thyroid - stimulating hormone were normal . intact parathyroid hormone ( pth ) level was 34 pg / ml ( normal , 15 - 65 pg / ml ) , serum calcium level was 9.8 mg / dl ( normal , 8.4 - 10.2 mg / dl ) and phosphorous was 4.3 mg / dl ( normal , 2.6 - 4.5 mg / dl ) . sestamibi scintigraphy was performed and it did not show any focal uptake ( figure-2 ) . sestamibi scintigraphy shows no focal uptake for parathyroid disease fine needle aspiration ( fna ) was performed under ultrasound guidance ; 5 ml clear colorless fluid was removed and complete collapse of cyst was obtained . cytological examination of the fluid was acellular , however , intact pth level of the fluid was 261 pg / ml . because of no evidence of hyperparathyroidism , conservative follow - up was decided . after six months of initial aspiration , there was no recurrence either physical examination or ultrasound evaluation . pc is rare clinical entity and about 300 cases have been reported in the literature up to this time . in 1880 , sandstrom reported first description of pc and goris reported the first successful resection of a cervical pc in 1905 ( 1 ) . several theories have been suggested for the development of pc including persistent embryologic remnant of pharyngeal pouches , an accumulation of secretions , enlargement of pre - existing microcysts and cystic degeneration of parathyroid adenoma ( 3 ) . ippolito described the compatibility between the embryologic remnant theory and 38 true pcs , in the one of the largest case series in the literature ( 4 ) . various combinations of different tissues as lymphoid , thymic , salivary , adipose , mesenchymal , were found in the cyst wall and these findings were suggestive of branchial origin . as compatible with this theory , some pcs arise from a pre - existing adenoma or a hyperplastic gland , however these are not true cysts . they consist of cystic degeneration of pre - existing lesion , therefore , usually presenting with hyperparathyroidism . traditionally , pcs are classified as functional or nonfunctional , the former being associated with clinical hyperparathyroidism . nonfunctional cysts are more common and the majority of patients , nearly 91% , have nonfunctioning cysts ( 5 ) . functional cysts , derived from parathyroid adenomas that underwent central necrosis and degeneration and account for 1% of all cases of hyperparathyroidism ( 6 ) . symptoms of nonfunctional cysts depend on the compression of neighboring structures ; therefore they are usually asymptomatic and found incidentally . neck swelling may be associated with dysphagia , odynophagia and paralysis of the recurrent laryngeal nerve ( 7 ) . rarely , cysts occur in the mediastinum and patients are admitted with respiratory symptoms . in the ippolito s case series , most common presentation was an asymptomatic cystic lesion that was detected incidentally during cervicotomy to treat a thyroid nodule . the location of the cysts differs between the two groups . for the nonfunctioning cysts , the inferior glands are most commonly involved , with the left - sided predominance . however , functional cysts have been located anywhere from the angle of the mandible to the mediastinum . in contrast to our knowledge , mccoy and colleagues reported that functional pcs are much more common than nonfunctional pcs and they have an equal affinity for superior and inferior glands ( 8) . our presented patient did not have any considerable symptom . ultrasonography , computerized tomography or magnetic resonance imaging can help to distinguish whether the mass is solid or cystic , however differentiating of thyroid tissue from parathyroid tissue are often experience dependence ( 6 ) . when intracystic fluid is water - clear and colorless , it is very suggestive of a parathyroid origin ( 9 ) . evaluation of the intracystic level of pth is more important than the appearance of the fluid . pth levels are increased in all pcs independently of whether they are functioning or nonfunctioning . both the carboxy - terminal pth ( inactive form of pth ) and intact pth ( bioactive form ) levels may be elevated . however , it is recommended that carboxy - terminal pth rather than the intact pth is requested on fluid obtained from a suspected parathyroid mass ( 10 ) . because of the correlation between the number of oxyphil cells and abnormal parathyroid tissue visualization in sestamibi scintigraphy , it rarely yields positive results for pcs . for the presented case , after suspicion for the pc , when a mass was detected on the ultrasonographic evaluation , fna was performed ; physical characteristics and pth level of the fluid confirmed the diagnosis of pc . fna with cystic fluid assay for pth levels represents the approach of choice for both diagnosis and the initial treatment . sclerosing therapy can be used as an alternative therapy by ethanol or tetracycline ; however , it may be associated with many complications as neck pain , neurotoxicity and recurrent nerve palsy . if repeated aspiration is unsuccessful , cyst is symptomatic or a functional cyst is present , surgical resection is the best option ( 3,4,7 ) . however , mccoy recommends the surgical therapy for all pcs regardless of functional status because of the low morbidity of surgery . for presented case , we have preferred the conservative approach by aspiration , follow - up and re - aspiration when necessary . after the definitive diagnosis , this approach is the best option for asymptomatic , nonfunctional cyst regardless of its size . in conclusion , pcs are rare lesion and often considered as thyroid cysts . diagnosis is best made by monitoring serum calcium levels and sending cyst fluid for pth analysis . therefore , pcs must be included and be remembered within the differential diagnosis of all neck swelling .
the differential diagnosis of cystic cervical masses includes cystic thyroid disease or some embryological diseases . 
 parathyroid cyst is one of the less common causes of the cervical masses . 
 the swedish anatomist sandstrom reported the first description of parathyroid cyst in 1880 . 
 up to date , only about 300 cases have been reported in the world literature . 
 they may be functional or nonfunctional , depending on the presence or absence of the hyperparathyroidism and treatment options vary for both presentations . particularly , nonfunctional cysts are often considered as thyroid cysts . 
 diagnosis is best made by monitoring serum calcium levels and sending cyst fluid for parathormone analysis.we herein report a patient diagnosed with a parathyroid cyst who had received the diagnosis of goitre at other institute ; including a review of the literature .