INTRODUCTION
Primary hyperparathyroidism (pHPT) is a pathology characterized by excessive secretion of parathyroid hormone from one or more parathyroid glands, leading to hypercalcemia and hypophosphatemia, usually caused by adenomas (1). Although 90% are sporadic, 10% may be hereditary (2). The parathyroid gland is typically found in four locations, two on each side of the thyroid gland; however, in 15-20% of cases, the parathyroid gland or adenomas may be ectopically located (3). The mediastinum is one such ectopic site for parathyroid adenomas (3). Retrospective studies have shown that functional mediastinal parathyroid adenomas are present in 1-3% of patients undergoing parathyroidectomy (3,4).
Most mediastinal parathyroid adenomas are located in the upper mediastinum, and a cervical incision with sub-flap progression is often sufficient as a surgical strategy. However, in approximately 10% of cases, sternotomy may be required for the surgery of mediastinal parathyroid adenomas (5). Inadequate surgical treatment and incomplete resection reduce the cure rate, and the relatively low success of reoperations affects the morbidity and mortality of patients (6). Thus, mediastinal parathyroid adenomas require meticulous management and specialized endocrine surgery operations where intraoperative strategy changes may be necessary. This report presents an example of managing a mediastinal parathyroid adenoma that caused secondary symptoms in the patient.
CASE REPORT
A 72-year-old male patient was under follow-up in the urology clinic due to a history of recurrent kidney stones. After presenting to the hospital with sudden colic attacks, the patient developed grade 3 hydronephrosis secondary to multiple stones and entered acute renal failure. During hospitalization, serum calcium levels were found to be 11.9 mg/dl. Imaging studies were ordered for the patient with elevated parathyroid hormone levels. Neck ultrasonography revealed no adenomas in normal parathyroid locations, nor were thyroid nodules detected. Technetium-99m sestamibi scintigraphy revealed an 8 cm x 4 cm lesion with high uptake in the retrosternal area, consistent with a parathyroid adenoma. No intrathyroidal or peri-thyroidal uptake was observed.
After emergency treatment in the urology clinic and stabilization of acute renal failure, the patient was transferred to the general surgery clinic for preoperative preparation. Thoracic computed tomography revealed a mass extending superolateral to the aortic arch in the retrosternal area. Preoperative magnetic resonance imaging (MRI) identified the lesion’s proximity to the aortic arch and its branches within adjacent fatty planes, and surgery was planned.
Under general anesthesia in the supine position, with the neck hyperextended for maximum visibility, a 6 cm Kocher incision was made from the sternal notch through the skin and subcutaneous tissues. The strap muscles were dissected at the midline, entering the thyroid compartment. The right thyroid gland was mobilized medially to locate the superior and inferior parathyroid glands on that side.
The procedure was repeated on the left side. After thorough examination of all four glands, no adenomas or hyperplastic changes were observed. Dissection proceeded inferiorly to the thymus region under the thyroid.
When palpation and blunt dissection failed to identify the adenoma, a partial superior sternotomy was planned in collaboration with the cardiovascular surgery team. After a 5 cm sternotomy, further exploration revealed the adenoma adhered to the sternum within fatty tissue. The adenoma was isolated from surrounding tissues using sharp and blunt dissection. It was excised en bloc with a LigaSure Atlas vessel sealing device (Valleylab; Tyco Healthcare Group LP, Boulder, CO).
The adenoma was sent for intraoperative pathological evaluation, confirming parathyroid adenoma. Postoperative serum PTH levels showed a >50% decrease, indicating successful excision. A suction drain was placed through the lateral end of the Kocher incision into the upper mediastinum. Hemostasis was confirmed, and the wound was closed appropriately.
The patient's postoperative intact parathyroid hormone level decreased to 46 pg/mL.
DISCUSSION
The first parathyroidectomy for a parathyroid adenoma, the most common pathology in primary hyperparathyroidism, was performed in 1925 by Felix Mandl for his patient Charles E. Martell (7). Parathyroid adenoma in this case led to severe osteitis fibrosa cystica (7). The procedure involved bilateral neck dissection, exploration of all four parathyroid glands, and excision of the gland with the adenoma (7). Since parathyroid hyperplasia was identified by Albright et al. in 1934, the understanding of parathyroid pathophysiology and surgical techniques has advanced significantly (8).
Primary hyperparathyroidism (pHPT) is characterized by dysregulation of calcium metabolism due to autonomous PTH production by one or more parathyroid glands (9). pHPT is the third most common endocrine disorder, after diabetes and thyroid diseases, and is the most common cause of hypercalcemia in outpatients (10). Unlike secondary or tertiary hyperparathyroidism, pHPT occurs without renal failure or a history of kidney transplantation, and is primarily caused by parathyroid adenomas (9,10). Approximately 85% of adenomas are single, 5% are double, 9-10% involve multiple hyperplasias, and less than 1% are associated with parathyroid carcinoma (11).
Ectopic hyperfunctioning parathyroid tissue is found in 11-25% of cases, with the most common ectopic location being along the paraesophageal groove (11). The development of mediastinal parathyroid glands can be explained by two different mechanisms. In one scenario, parathyroid glands descend into the chest due to gravity and negative intrathoracic pressure during expiration after developing adenomas (12). Alternatively, mediastinal parathyroid adenomas may arise embryologically from inferior or supernumerary (fifth) parathyroid glands (12).
Preoperative imaging techniques play a critical role in determining surgical strategy and predicting success (6,14). Correlating neck ultrasound with scintigraphy helps identify autonomous functioning glands (15). Even if imaging fails to localize an adenoma, surgical indications remain unchanged (16).
For ectopic mediastinal parathyroid glands, extensive resection may be necessary to ensure a cure, even though minimally invasive techniques are emerging (6,12). Traditional methods such as median partial or total sternotomy, or thoracotomy, remain critical in managing mediastinal parathyroid adenomas (16).
Our patient successfully underwent adenoma excision starting with a Kocher incision and proceeding to partial sternotomy without complications. Postoperative follow-up revealed no recurrence or hypercalcemia-related symptoms at one year.
