Interpretative Problems and Preparative Technique Influence Reliability of Intraoperative Parathyroid Touch Imprints

Context: Identification of parathyroid tissue (PT) is crucial during parathyroid and thyroid surgery. Touch imprint preparation (TIP) examination is potentially a more time-effective and less labor-intensive approach than frozen section examination for identification of PT during intraoperative consultation. However, the reliability of PT-TIP remains controversial, and this fact has hindered its adoption as a replacement for frozen section examination.

Objective: To assess the factors contributing to the relative lack of reliability of TIP in a retrospective study.

Methods: Fifty randomly selected, alcohol-fixed, hematoxylin-eosin- and/or Diff-Quik-stained TIPs of specimens that had been submitted to confirm PT during intraoperative consultation were retrospectively reviewed by 5 observers. The observers were blinded to the final interpretation (based on hematoxylin-eosin-stained permanent sections), which included PT in 39 (78%) of the 50 specimens, thyroid in 9 (18%), lymph node in 1 (2%), and adipose tissue 1 (2%). Cases in which a unanimous diagnosis was not attained were re-reviewed by 3 observers.

Results: Of 50 TIPs reviewed, a unanimous diagnosis was rendered in 33 cases (66%), including 27 (69%) of 39 PT cases, 5 (56%) of 9 thyroid cases, and the 1 lymph node case. Cytologic features observed in the TIPs that were unanimously accepted as being diagnostic of PT included the presence of small uniform cells in isolation or in small groups, round to oval nuclei, salt-and-pepper chromatin, occasional naked nuclei, and delicate vacuoles both within the cytoplasm and in the background. Re-review of the 17 remaining TIPs cases, in which diagnostic unanimity was not achieved, demonstrated that factors hindering assessment of the TIPs included hypocellularity (n = 5 cases), air-drying effect (n = 4), hemorrhagic background (n = 4), and presence of PT cells in follicular (thyroid-like) arrangements (n = 4).

Conclusions: The major factors influencing reliability of TIP of PT during intraoperative consultation are related primarily to interpretative problems and preparative technique. Awareness of interpretative problems and attention to preparation of TIPs may further enhance the accuracy of TIP during intraoperative consultation.