Intrathyroid parathyroid adenoma: incidence and location--the case against thyroid lobectomy.

OBJECTIVE: It has been taught that a missing parathyroid adenoma can be within the thyroid. Therefore, thyroid lobectomy is appropriate when an adenoma cannot be found. Unfortunately, this technique is often futile. The purpose of this study is to examine the frequency of unsuccessful thyroid lobectomy in parathyroid surgery and to look at the true incidence and location of intrathyroid parathyroid adenomas (iT-PAs).

STUDY DESIGN: A retrospective chart review of 11,163 patients undergoing parathyroid surgery identifying the location of more than 40,000 parathyroid glands.

SETTING: A tertiary care center specializing in parathyroid surgery.

SUBJECTS AND METHODS: A total of 1163 reoperations for persistent primary hyperparathyroidism (PHPT) were examined for the incidence and outcomes of thyroid lobectomy performed to find iT-PA. A second study examined 10,000 patients undergoing first-time parathyroidectomy to classify the location and incidence of iT-PA.

RESULTS: Thyroid lobectomy had been previously unsuccessfully performed in 77% cases of PHPT undergoing reoperation. Two or fewer glands were found in 82% prior to lobectomy. The adenoma was subsequently found on the lobectomy side in 64% and on the opposite side in 36%. True iT-PA occurred in only 0.7% of 10,000 primary cases. Another 1.2% were closely adherent to or partially within the thyroid substance. The most common location was the lower lateral quadrant of the thyroid.

CONCLUSION: The incidence of true iT-PA is less than 1%, occurring in predictable locations. Thyroid lobectomy for a missing parathyroid adenoma is typically unsuccessful and should only rarely, if ever, be performed.