The author has no conflict of interest.
Ectopic Parathyroid Tumor in the Sternohyoid Muscles: Supernumerary Gland in a Patient With MEN Type 1†
Article first published online: 2 MAY 2005
Copyright © 2005 ASBMR
Journal of Bone and Mineral Research
Volume 20, Issue 8, pages 1478–1479, August 2005
How to Cite
Miura, D. (2005), Ectopic Parathyroid Tumor in the Sternohyoid Muscles: Supernumerary Gland in a Patient With MEN Type 1. J Bone Miner Res, 20: 1478–1479. doi: 10.1359/JBMR.050502
- Issue published online: 4 DEC 2009
- Article first published online: 2 MAY 2005
- Manuscript Received: 29 DEC 2005
- Manuscript Accepted: 27 APR 2005
- Manuscript Revised: 16 APR 2005
Successful parathyroidectomy requires surgeons to find, recognize, and excise the abnormal parathyroid glands based on their knowledge of anatomy, embryology, and their experience in parathyroid surgery. The location of the parathyroid glands varies widely as a result of a differing degree of migration during embryologic development. Superimposed on this anatomic heterogeneity is the displacement of parathyroid glands that occurs as the parathyroid tumor enlarges as part of the process of developing hyperparathyroidism. Therefore, in some patients with hyperparathyroidism, parathyroid gland migration results in considerable displacement of parathyroid tumors. Awareness of the common pathways of migration is therefore invaluable in parathyroid surgery.
The present patient was a 47-year-old man with primary hyperparathyroidism (PHPT) and a family history of multiple endocrine neoplasia (MEN) type1 (affecting his mother and sister). He had no significant past medical history and had never undergone cervical procedures such as fine needle aspiration biopsy or acupuncture. Laboratory investigations revealed the following: serum calcium, 11.2 mg/dl; phosphate, 4.2 mg/dl; intact PTH, 105.2 pg/ml; renal function, normal. Preoperative CT of the neck revealed a hyperdense tumor (15 × 3 mm in size) superficial to the strap muscles in the subcutaneous fat tissue (Fig. 1), in addition to two tumors also detected on both ultrasound and sestamibi scintigraphy. He underwent total parathyroidectomy and autotransplantation of parathyroid tissue into the forearm. At neck exploration, a well-circumscribed nodule was found superficial to the sternohyoid muscle fibers, just beneath the sternohyoid fascia (Fig. 2). After removing this nodule (274 mg), four nonectopic enlarged parathyroid tumors (left superior, 2040 mg; left inferior, 72 mg; right superior, 188 mg; and right inferior; 60 mg) were also removed, and 30 mg of parathyroid tissue was autotransplanted into the forearm. The final pathologic report revealed that all resected lesions, including the sternohyoid nodule, were hyperplastic parathyroid neoplasms. Postoperatively, serum calcium level decreased promptly to 7.8 mg/dl (reference range, 8.8–10.2 mg/dl). Parathyroidectomy was successful, and although parathyroid autotransplantation had been performed, the patient required the active form of vitamin D (alfacalcidol 1 μg/day) for 8 years. At 8 years postoperatively, the intact PTH level in the basilic vein was 630.9 pg/ml on the side of autotransplantation and 14.1 pg/ml on the other side, showing a functioning parathyroid autograft, and the blood calcium level was 9.0 mg/dl.
Ectopic parathyroid glands are most commonly located in the mediastinum and the thyroid gland. Wang(1) dissected 645 normal adult parathyroids from 160 cadavers and described ectopic parathyroid occurring in the subcapsular portion of the thyroid, the thymic tongue, and the mediastinum, and rarely behind the esophagus, in the pharynx, and in the vagus nerve. Most of these unusual locations were explained on the basis of anomalous branchial cleft migration. Thompson et al.(2) followed 273 patients with PHPT for 4 years and found true intrathyroid parathyroid glands in 3%. Failure of an inferior parathyroid gland to descend during embryonic development may result in a gland located higher up in the neck, even above the upper thyroid pole; these glands are usually surrounded by a remnant of thymic tissue (an undescended parathymus). The incidence of supernumerary glands varies from 2.5% to 22%,(3, 4) with most of these glands considered to be either rudimentary or divided. We could not elucidate the origin of this intriguing supernumerary and aberrant parathyroid tumor, because thymic tissue was not found in the tumor and because it did not derive its arterial supply from the inferior or superior thyroid artery, but from the arterial supply to the sternohyoid muscles. To the best of our knowledge, ectopic parathyroid gland has not previously been discovered in the sternohyoid muscles. After parathyroid or thyroid surgery, whereas autotransplanted normal parathyroid tissue may rarely develop primary hyperparathyroidism, hyperplastic parathyroid tissue autotransplanted often recurs in patients with familial primary hyperparathyroidism or MEN syndromes and secondary hyperparathyroidism for renal failure. Moreover, careless handling of parathyroid tumor can result in parachromatosis, although this is rare.(5) Although we initially considered that this ectopic gland might have been disseminated by an unrelated cervical procedure such as fine needle aspiration biopsy or acupuncture, the patient had no history of these interventions or of previous neck exploration.
In primary hyperparathyroidism, during preoperative localization and neck exploration, greater awareness of the possibility of aberrant parathyroid in the neck and elsewhere may help to avoid a failed operation. Unusual location of an abnormal gland such as in the sternohyoid muscles should also be considered.
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