Hyperfunctioning Intrathyroidal Parathyroid Cyst

Michael R. Rickels, Jill E. Langer and Susan J. Mandel

Division of Endocrinology, Diabetes and Metabolism, Departments of Medicine (M.R.R., S.J.M.) and Radiology (J.E.L., S.J.M.), University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104

Address all correspondence and requests for reprints to: Susan J. Mandel, M.D., M.P.H., Hospital of the University of Pennsylvania, 1 Maloney, Endocrine Clinic, 3400 Spruce Street, Philadelphia, Pennsylvania 19104. E-mail: smandel{at}mail.med.upenn.edu.

A 54-yr-old man had nephrolithiasis attributed to primary hyperparathyroidism based on elevated concentrations of serum calcium [11.4 mg/dl (2.8 mmol/liter); normal, 8.5–10.6 mg/dl (2.1–2.6 mmol/liter)], serum intact PTH [151 pg/ml (16 pmol/liter); normal, 12–72 pg/ml (1.3–7.6 pmol/liter)], and 24-h urine calcium [271 mg (6.8 mmol); normal, <200 mg (5.0 mmol)]. Figure 1Go depicts the preoperative imaging. A planar parathyroid scan performed 2 h after the administration of technetium sestamibi demonstrated persistent uptake at the right lower pole of the thyroid (Fig. 1AGo, arrow), a result consistent with the presence of a parathyroid adenoma. An ultrasound evaluation demonstrated a 1.7-cm predominantly cystic nodule in the right lower pole of the thyroid (Fig. 1BGo, circle), and ultrasound-guided fine-needle aspiration yielded epithelial cells possibly representing parathyroid tissue. A subsequent needle pass attempting to sample the cyst fluid yielded bloody material of insufficient quantity to analyze for intact PTH.



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FIG. 1. A parathyroid scan demonstrated persistent uptake at the right lower pole of the thyroid (A, arrow), and a sagittal ultrasound view demonstrated a 1.7-cm predominantly cystic nodule in the right lower pole of the thyroid (B, circle).

 
A right hemithyroidectomy revealed a 1.8-cm parathyroid cyst in the lower lobe. Two months postoperatively, the concentrations of serum calcium [9.0 mg/dl (2.2 mmol/liter)], serum intact PTH [34 pg/ml (3.6 pmol/liter)], and 24-h urine calcium [165 mg (4.1 mmol)] were normal.

Parathyroid cysts are uncommon causes of neck or mediastinal masses, and only rarely result in primary hyperparathyroidism (1, 2, 3). They have been mistaken for cystic thyroid nodules, branchial cleft cysts, or thyroglossal duct cysts (1). The diagnosis of a parathyroid cyst can be made either by finding a markedly elevated level of intact PTH in the cyst fluid (1, 2) or by the pathologic identification of parathyroid epithelium within the cyst wall (1, 3). A parathyroid cyst may be the cause of primary hyperparathyroidism when preoperative imaging demonstrates an intra- or perithyroidal cystic mass lesion.

See Fig. 1Go on following page.


    Footnotes
 
M.R.R. was supported by National Institutes of Health Grant K12 RR017625, the University of Pennsylvania School of Medicine Training Grant in Patient-Oriented Research.

Received October 22, 2003.

Accepted November 14, 2003.


    References
 Top
 References
 

  1. Apel RL, Asa SL 2002 The parathyroid glands. In: LiVolsi VA, Asa SL, eds. Endocrine pathology. Philadelphia: Churchill Livingstone; 135–136
  2. Safran D 1998 Functioning parathyroid cyst. South Med J 91:978–980[Medline]
  3. Jarnagin WR, Clark OH 1998 Mediastinal parathyroid cyst causing persistent hyperparathyroidism: case report and review of the literature. Surgery 123:709–711[CrossRef][Medline]




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