Intraoperative identification of parathyroid tissue: a comparative validity study of frozen section, cytology, and reflected-light diagnostic methods

Abstract

Background Surgery is the main line of treatment for hyperparathyroidism, but preliminary localization of the lesion is essential. This could be accomplished preoperatively by radiographic methods (isotope scans and ultrasonography) or intraoperatively by pathologic methods, namely, frozen section, cytology, and reflected-light microscopy. Aim To compare the diagnostic accuracy of the intraoperative pathologic methods when used singly or combined. The study was done on 30 (10 parathyroid tissue and 20 nonparathyroid tissue) tissue samples, obtained from nine patients. Modifications were made on a monocular microscope to allow transmitted-light, reflected-light, and digital photography. Results When used alone, the diagnostic accuracy was 96.6% for frozen section, 86.6% for cytology, and 80% for reflected-light microscopy. The combined use of cytology with reflected-light microscopy increased the diagnostic accuracy to 93.3%, with good concordance with the accuracy of frozen section combined with cytology (κ ratio 0.651). Diagnostic errors were mainly owing to the difficulty to differentiate thyroid from parathyroid tissue. Conclusion In specialized centers, frozen section combined with cytology is the method of choice for the intraoperative diagnosis of parathyroid tissue. Conversely, in developing countries, where frozen section equipment is usually not available, combination of reflected-light microscopy and cytology is a good, inexpensive, rapid and effective alternative. However, proper training is needed for these methods to ensure an accurate diagnosis.