Liquid-based cytology in the fine needle aspiration of parathyroid lesions: a comparison study with the conventional smear, ThinPrep, and SurePath.

Liquid-based cytology (LBC) has been progressively used for evaluating fine needle aspiration (FNA) specimens. However, limited studies have examined LBC in FNA of parathyroid lesions. We retrospectively reviewed 24 FNA specimens of parathyroid lesions, including 6 specimens prepared by conventional smear, 12 specimens prepared using ThinPrep method, and 6 specimens prepared using SurePath method. The 18 LBC specimens were also used for cell block preparation and immunostaining for parathyroid hormone (PTH). LBC specimens more frequently showed variable cellularity; microfollicular structure; bubbly or vacuolated cytoplasm; and small, round cells with distinct borders compared to specimens prepared by conventional smear. ThinPrep specimens showed a clean background and fewer isolated cells and naked nuclei compared to specimens prepared using the other methods. SurePath specimens showed many white blood cells in the background and more scattered single cells and naked nuclei compared to ThinPrep specimens. Specimens prepared using the 3 methods often showed colloid-like material but did not contain dense globular colloidal structures. White blood cells in the background of LBC specimens serve as useful indicators for estimating cell size. The nuclear size of parathyroid cells was similar to or smaller than that of inflammatory cells in the background. Cell block sections showed definite histological features of the parathyroid tissue and strong positive immunostaining for PTH. Awareness of these cytologic features of parathyroid FNA specimens prepared using ThinPrep and SurePath methods may help in preventing misdiagnosis. Cell block preparation and PTH immunostaining should be performed for the definitive diagnosis of parathyroid lesions.