Supernumerary intravagal parathyroid hyperplagia

In the April issue of Surgery, Hung et al (Surgery 2002;131:359-361) described a case of supernumerary intravagal parathyroid hyperplasia. In their report they alleged that only 3 prior cases of hyperparathyroidism resulting from intravagal parathyroid tissue had been reported. ^{,  ,}  Furthermore, they claimed that no cases of supernumerary intravagal parathyroid hyperplasia had been described and that their report was the first to date. Unfortunately, each of these claims was inaccurate. In April 2001 we reported 2 additional cases of intravagal parathyroid adenomas (not accounted for by Hung et al). One of our patients had tertiary hyperparathyroidism, the other had primary hyperparathyroidism. In both cases, we reported that the hyperplastic parathyroid tissue was supernumerary in character. The work of pathologist Gilmour, Lack, and colleagues supported our findings. In 1937 Gilmour described accessory parathyroid tissue within the ganglion of the vagus nerve. In Gilmour's dissection of stillborn infants, the third branchial pouch, which gives rise to the inferior parathyroid glands, was found to be in direct relation to the ectodermal structures, particularly the vagus nerve. More recently in 1988, Lack et al reported that in his postmortem study of vagus nerves from children under the age of 1 year, he found parathyroid chief cells located either adjacent to the epinerium or perineurium. Both Gilmour, Lack, and colleagues postulated that the microscopic parathyroid tissue probably represented accessory or supernumerary tissue. This is exactly what we found in each of the cases we reported. Both adenomas were located in the vagus nerve and represented supernumerary tissue. Each adenoma was at a level below vagal ganglions and was several centimeters below the carotid bifurcation. Indeed, in a review of all 5 cases described to that point, the intravagal parathyroid tissue was always supernumerary. Based on this finding, and the pathologic work of Gilmour, Lack, and colleagues, we were the first to report that intravagal adenomas, although rare, do occur and invariably represent supernumerary tissue near the level of the carotid bifurcation, probably originating from the third branchial pouch. Given this, we have previously recommended that examination of the vagus nerve should always be considered when 4 normal glands are found. Thus, not only is the report by Hung et al of supernumerary intravagal parathyroid hyperplasia not novel, it is exactly what we would have predicted.