Parathyromatosis.

Parathyromatosis is a rare condition that causes persistent or recurrent hyperparathyroidism. It is characterized by the finding of multiple rests of hyperfunctioning parathyroid tissue in the neck and mediastinum. Patients with this condition typically develop recurrent or persistent hypercalcemia.

This entity can exist as a primary or secondary condition. Primary parathyromatosis occurs in patients with multiple endocrine neoplasia (MEN), most commonly MEN type 1. Genetic abnormalities in patients with MEN syndromes cause parathyroid tissues to develop into tiny rests of parenchymal cells scattered throughout the neck and mediastinum. Secondary parathyromatosis, which is more common, develops following surgical exploration of the neck. It has been proposed that during removal of hypercellular parathyroid tissue, some tissue is spilled and later becomes hyperplastic.

Macroscopically, parathyromatosis manifests as soft, yellow-white nodules, ranging in size from microscopic to 2 cm and distributed throughout the soft tissues (skeletal muscle and fat) of the neck, including retrosternal, superior mediastinal, and posterior pharyngeal tissues. This pattern of growth and the adherence to surrounding structures mimic carcinoma (figure, A), although there is no vascular invasion or desmoplastic reaction. Histologically, the cells resemble chief cells and are uniform, with clear to amphophilic cytoplasm surrounding small, hyperchromatic nuclei (figure, B). Changes associated with carcinoma--such as mitotic figures, cellular pleo morphism, desmoplastic reaction, or vascular/perineural invasion--are not seen.

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Parathyromatosis should be considered in the differential diagnosis for a patient with recurrent hyperparathyroidism, hypercalcemia, a history of MEN, or previous neck surgery. Treatment is challenging because it is often difficult to identify and remove all of the abnormal rests of parathyroid tissue. If hypercalcemia persists after surgery, periodic bisphosphonate therapy may help lower serum calcium levels.

Suggested reading

Baloch ZW, Fraker D, LiVolsi VA. Parathyromatosis as cause of recurrent secondary hyperparathyroidism: A cytologic diagnosis. Diagn Cytopathol 2001;25:403-5.

Kollmorgen CF, Aust MR, Ferreiro JA, et al. Parathyromatosis: A rare yet important cause of persistent or recurrent hyperparathyroidism. Surgery 1994;116:111-15.

Reddick RL, Costa JC, Marx SJ. Parathyroid hyperplasia and parathyromatosis. Lancet 1977; 1:549.

Janette M. Carpenter, MSN, FNP; Peter G. Michaelson, MD; Thomas K. Lidner, MD; Michael L. Hinni, MD

From the Department of Otolaryngology--Head and Neck Surgery, Keck School of Medicine, University of Southern California, Los Angeles (Ms. Carpenter); the Department of Otolaryngology--Head and Neck Surgery, Wright-Patterson Air Force Base Medical Center, Dayton, Ohio (Dr. Michaelson); the Department of Otolaryngology--Head and Neck Surgery (Dr. Hinni) and the Department of Pathology (Dr. Lidner), Mayo Clinic, Scottsdale, Ariz.