Parathyroid/Bone Disorders
Jenny Q. Dai-Ju, PhD, MBBS (she/her/hers)
Assistant Clinical Professor
University of California, Irvine
Irvine, California, United States
Parathyromatosis is a rare cause of recurrent hypercalcemia and hyperparathyroidism after parathyroidectomy for primary hyperparathyroidism. It is described as a hyperfunctioning nodule of parathyroid tissue in the neck and/or mediastinum. Although parathyromatosis is considered a benign pathology finding, achieving complete excision is challenging due to difficulties in tumor localization.
Case(s) Description :
A 36-year-old female with a history of kidney stones was evaluated in our endocrine clinic for hypercalcemia (12.1 mg/dL) and hyperparathyroidism (PTH-I 125 pg/mL). The 24-hour urine calcium was above the normal range (359 mg). Past medical history included a right parathyroidectomy for hyperparathyroidism at age 18. Calcium and PTH-I levels were normal soon after the initial surgery. The patient did not follow up until a recent episode of nephrolithiasis. Parathyroid ultrasound, Sestamibi scan, and four-dimensional parathyroid CT failed to localize a parathyroid adenoma. A bedside ultrasound exam identified a 1.09 cm hypoechoic mass associated with the left infrahyroid muscles next to midline. The patient underwent a re-do parathyroid surgery and a 1.3 cm tumor embedded in the soft tissues and anterior surface of the left sternohyoid muscle was removed. Intraoperative parathyroid hormone dropped from 458 to 115 pg/mL. Hypercellular parathyroid tissue was present within skeletal muscle and fibrous tissue in pathology analysis. Immunostaining was positive for PTH and negative for TTF-1, which confirmed parathyromatosis. Ten months after the second operation, the patient’s PTH and serum calcium levels remained normal.
Discussion :
Parathyromatosis is displaced parathyroid tissue in the neck and mediastinum due to the seeding of parathyroid cells and overgrowth into hyperfunctioning nests of tissue. Small-sized foci with surrounding tissue may not be detectable on ultrasound, Tc99m sestamibi scintigraphy or CT. Although parathyromatosis is rarely reported, it should still be included for differential diagnoses in cases of recurrent hypercalcemia and primary hyperparathyroidism.