Intraoperative confirmation of parathyroid tissue during parathyroid exploration: a retrospective evaluation of the frozen section.

Although the frozen section is widely used to identify tissue type during parathyroid exploration in patients with hyperparathyroidism, questions regarding its accuracy have been raised. Frozen section error has been identified as a significant factor contributing to surgical failure. The purpose of this study was to establish the accuracy of frozen section in this setting and to identify pitfalls underlying frozen section error. The final pathologic diagnoses were compared with the paired frozen section diagnoses for all patients who underwent parathyroid exploration at this institution in the period between 1984 and 1997. For those cases in which a discrepancy was identified, the original histopathology slides and the medical records were reviewed. Of the 1579 frozen sections, a definitive and accurate diagnosis could not be determined in 20 cases (1.3%); in 7 (0.4%), the frozen section diagnosis was deferred, and in the other 13 cases, the frozen section diagnosis was incorrect. Overall accuracy rate was 99.2% after deferred cases were excluded. Frozen section artifact, sampling error, and judgmental error contributed to deferred or incorrect diagnoses. Several features confounded the distinction between parathyroid and thyroid tissue in 10 cases: the coexistence of parathyroid and nodular thyroid disease; intrathyroidal parathyroid glands showing conspicuous follicle formations or abundant oncocytic cells; and thyroid nodules with fatty stroma. The frozen section is a highly reliable means of identifying tissue type during parathyroid exploration. In exceptional cases, however, the distinction between parathyroid and thyroid tissue may not be possible owing to a striking overlap seen at the clinical, gross, and microscopic levels.