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Unusual presentation of primary hyperparathyroidism: report of three cases
© Huang et al. 2015
Received: 8 October 2014
Accepted: 2 June 2015
Published: 16 July 2015
Primary hyperparathyroidism is an endocrinopathic condition characterized by hypersecretion of parathyroid hormone. Excess parathyroid hormone results in an altered state of osseous metabolism involving bone resorption and tissue change known as osteitis fibrosa cystica, which is the end stage of primary hyperparathyroidism. Osteitis fibrosa cystica is associated with the development of brown tumors, which are rare because hyperparathyroidism is now usually diagnosed and treated before symptoms develop. Brown tumors are rarely the first symptom of hyperparathyroidism and can occasionally be mistaken for malignancy.
We herein report three cases of primary hyperparathyroidism with an unusual presentation of brown tumors. All three patients were Asian. In the first case, a 42-year-old man was admitted with a mass mimicking a malignant bone neoplasm in the right mandible as the first manifestation of primary hyperparathyroidism. The second case involved a 25-year-old man admitted with a fracture of his right femur. The third case involved a 43-year-old man with multiple brown tumors in both lower limbs. All three patients underwent successful parathyroidectomy for parathyroid adenomas; one case was complicated by a papillary thyroid carcinoma.
Complete evaluation of the medical history and biochemical and radiographic findings is necessary to achieve a correct diagnosis and avoid unnecessary bone resections in patients with primary hyperparathyroidism.
KeywordsPrimary hyperparathyroidism Brown tumor Osteitis fibrosa cystica Giant cell tumor
The parathyroid glands secrete parathyroid hormone (PTH), which is involved in regulating the metabolism of calcium and phosphorus. PTH plays an important role in tooth development and bone mineralization and increases bone resorption. Excessive secretion of PTH is termed hyperparathyroidism (HPT), which is an endocrine condition categorized as primary, secondary, or tertiary. Primary HPT (PHPT) is an endocrinopathic condition characterized by hypersecretion of PTH, which may be caused by an adenoma (solitary or multiple), idiopathic hyperplasia, or a parathyroid carcinoma. Secondary HPT is caused by hypocalcaemia or vitamin D deficiency acting as a stimulus of excessive PTH production. Chronic renal failure is the main cause of secondary HPT. Tertiary HPT is caused by the development of autonomous parathyroid hyperplasia after long-standing secondary HPT, most often in patients with renal failure . Most cases of PHPT (80 %–85 %) are caused by a solitary adenoma, 15 % to 20 % are due to parathyroid gland hyperplasia, and <0.5 % are caused by parathyroid carcinoma [2, 3]. Renal calculi have been reported in 10 % to 25 % of cases, and the frequency of bone disease among patients with PHPT is 10 % to 20 % .
Skeletal involvement in classic PHPT is characterized by a strikingly high rate of osteoclastic bone resorption and is accompanied by a cellular repair process that results in the accumulation of fibrous stroma and connective tissue cells along with multinucleated giant cells. Thus, brown tumors have been described as resulting from an imbalance between osteoclastic and osteoblastic activity, resultant resorption with fibrous replacement of the bone, and eventual osteitis fibrosa cystica (OFC).
Brown tumors are reactive lesions and do not represent true neoplasms. They may be difficult to diagnose because they present clinically and radiologically as other diseases such as giant cell tumors, multiple bone metastases, or multiple myeloma [5, 6]. Moreover, from a histological perspective, differential diagnosis among brown tumors, giant cell granulomas, and giant cell bone tumors may be very difficult without an accurate and complete preoperative clinical evaluation.
Brown tumors involving the jaw bones as the first manifestation of PHPT and pathological fractures that lead to a diagnosis of PHPT are not commonly described [7–11]. We herein report three Asian patients with PHPT with an unusual first manifestation of brown tumors.
Laboratory data before and after parathyroidectomy in the three patientsPTH, parathyroid hormone; ALP, alkaline phosphatase; Ca, calcium; −, not available
Reference range, adults
PTH level (pg/ml)
Case 1: −
Case 1: 939.80
Case 1: 66.40
Case 2: −
Case 2: 1399.80
Case 2: 65.40
Case 3: −
Case 3: 1084.45
Case 3: 80.20
Ca level (mmol/L)
Case 1: 3.18
Case 1: 2.93
Case 1: 2.13
Case 2: 3.59
Case 2: 3.37
Case 2: 2.56
Case 3: 2.91
Case 3: 3.53
Case 3: 2.24
Phosphorus level (mmol/L)
Case 1: −
Case 1: −
Case 1: 0.75
Case 2: 0.78
Case 2: −
Case 2: 0.52
Case 3: −
Case 3: −
Case 3: −
Case 1: 422
Case 1: −
Case 1: −
Case 2: 1367
Case 2: −
Case 2: −
Case 3: 1154
Case 3: 387
Case 3: −
Case 1: 131
Case 1: −
Case 1: −
Case 2: 94
Case 2: 108
Case 2: 217
Case 3: 51
Case 3: 60
Case 3: 66
These findings suggested that PHPT initially manifested as a brown tumor of the jaw. Contrast MRI of the neck confirmed the existence of a 2.5-cm nodular mass on the lower right parathyroid (Fig. 1d). Mini-invasive parathyroidectomy was performed. Histopathology confirmed that the resected lesion was a parathyroid adenoma.
The patient recovered well postoperatively, and his serum calcium (2.13 mmol/L) and PTH (66.40 pg/ml) levels normalized within 1 week. Detailed biochemical data observed before and after parathyroidectomy are shown in Table 1. The patient was lost to long-term follow-up after clinical improvement.
Parathyroidectomy was performed, and the lesion was histologically confirmed to be a benign parathyroid adenoma. The patient recovered well postoperatively, and his serum calcium (2.08 mmol/L) and PTH (65.40 pg/ml) levels normalized within 2 weeks. The patient’s biochemical data before and after parathyroidectomy are shown in Table 1. Surgical intervention for the pathologic fracture was contraindicated because of serious osteoporosis. Thus, conservative treatment involving fracture reduction and splint fixation was performed. This patient was still being followed up at the time of this writing.
PHPT was suspected. Enhancement CT of the neck revealed a round mass measuring 2.7 × 1.4 cm behind and below the left thyroid lobe and a round lesion measuring 1.5 × 1.0 cm located in the left thyroid lobe (Fig. 3d). Parathyroidectomy was performed. Histological examination confirmed the diagnosis of adenoma of the left parathyroid gland and papillary thyroid carcinoma of the left thyroid lobe. Biochemical data observed before and after parathyroidectomy are shown in Table 1. After a review of bone slices, the final diagnosis was a brown tumor probably due to long-standing underestimated PHPT.
The incidence of PHPT is difficult to assess and may vary widely from 0.4 to 21.6 cases per 100,000 person-years [12, 13]. Additionally, racial or regional differences in the incidence and prevalence of PHPT may exist . The incidence of PHPT is nearly two or three times more common in women than in men [6, 14, 15]. In most patients with PHPT (80 %–85 %), the disease develops due to a parathyroid adenoma, in 15 % to 20 % due to parathyroid gland hyperplasia, and in <0.5 % due to parathyroid carcinoma [2, 3]. Before the 1970s, PHPT was a disease caused by recurrent kidney stones, brown tumors, neuromuscular dysfunction, and symptomatic hypercalcemia [16, 17]; today, it can be diagnosed in the early and asymptomatic period because of advances in blood analysis and a growing awareness of this disease [18–21]. However, normocalcemic HPT may be an early form of the disease [8, 22].
Although many systems are affected in patients with PHPT, the most pronounced alternations are observed in the bone. Classic skeletal lesions are bone resorption, OFC, and brown tumors. With the recent development of imaging and laboratory screening methods, however, hypercalcemia due to primary or secondary HPT can often be detected early, with a decrease in frequency of OFC and brown tumors. A brown tumor is the localized form of OFC . It is more common in people aged >50 than <50 years and three times more common in women than in men; the preferential locations are the facial skeleton (particularly the mandible)  and the ends of long bones and ribs . The incidence of brown tumors in patients with PHPT is 1.5 % to 1.7 % , and these tumors rarely present as the first manifestation of PHPT, as in our cases.
The term “brown tumor” is derived from the characteristic appearance of a brown-colored material within the cystic lesion, which is caused by high vascularity, hemorrhage, and hemosiderin deposits . Brown tumors are not true neoplasms, but they can be locally aggressive and mimic malignancies. In some cases, they may lead primarily to the differential diagnosis of other giant cell lesions (reparative giant cell granuloma, cherubism, aneurysmal bone cyst, or true giant cell tumor) or a metastatic lesion because of the rarity of multiple lesions of this type [5, 27, 28]. This was demonstrated in our first patient, in whom medical imaging findings suggested a malignant bone neoplasm.
On radiography and CT, brown tumors are seen as lytic lesions or sclerotic lesions with regular borders and no cortical disruption, periosteal reaction, or inflammatory signs . MRI shows variable intensities on T2-weighted images and intense enhancement on T1-weighted contrast images [9, 30]. The appearance on radiographs and CT is variable and not always specific and can mimic a malignant tumor [4, 5, 31]. In our first patient, the expansionary cystic bone lesion in the right mandible penetrated the cortex and formed a peripheral soft tissue mass, mimicking a malignant neoplastic lesion and thus confusing clinicians regarding the correct diagnosis and therapeutic management.
Some large bone defects increase the risk of spontaneous fracture, a rare complication of PHPT. The reported crude fracture rate in patients with PHPT has been documented as 15 per 1000 person-years (compared with 8 per 1000 in controls) . However, PHPT revealed by pathological fracture, as in our third patient, is extremely rare [24, 32].
Brown tumors exhibit no pathognomonic histological changes and are characterized by numerous giant cells, diffused or arranged in clusters, in a background of mononuclear oval-to-spindle stromal cells . These giant cells are similar to those in other giant cell lesions such as reparative giant cell granulomas, cherubism, and aneurysmal bone cysts. Therefore, distinguishing a brown tumor from other giant cell lesions on the basis of histological examination may be difficult [33, 34]. A definitive diagnosis is only possible by comparing the clinical manifestations and radiological and laboratory test results that differentiate the lesions.
The treatment of choice for PHPT is parathyroidectomy, and the best treatment of brown tumors is cure of the underlying PHPT [3, 17, 18]. However, the fracture should undergo curettage, associated enucleation, and stabilization in patients with large lesions or lesions that persistently grow despite treatment, persist for more than 6 months, disrupt the function of the affected organ, or are associated with previous fracture fragility [35–38]. Extensive bone resection was not performed for our third patient because he had serious osteoporosis, making surgical intervention a high-risk procedure. In some cases, resection is performed only to achieve a definitive diagnosis [5, 28, 38].
In summary, PHPT is now usually detected in the early and asymptomatic phase because of recent improvements in analytical techniques. A brown tumor is a benign clinical entity appearing as an extremely rare manifestation of HPT and an uncommon cause of pathological fractures, which can be difficult to distinguish from other tumors, tumor-like lesions, and metastatic disease. When a patient, especially a middle-aged patient, presents with unexplained lytic bone lesions or pathological fractures, surgeons, endocrinologists, and especially radiologists should be reminded of this unusual presentation of PHPT to avoid unnecessary surgical removal. Our cases highlight the importance of a thorough diagnostic work-up for PHPT. A definitive diagnosis is only possible upon completion of clinical, radiological, and biochemical analysis.
Written informed consent was obtained from the patients for publication of these case reports and any accompanying images. A copy of the written consent is available for review by the Editor of this journal. This study was approved by the ethics committee of the First Affiliated Hospital of Shantou University Medical College.
The authors gratefully acknowledge the assistance provided by Laura Smales for the revision of this manuscript.
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