Thyroid fine-needle aspiration: Smears versus liquid-based preparations

Abstract

T he sampling of tissue with needles for the purpose of investigating neoplastic processes has been reported over the past 160 years. 1,2 Until recently, smears, sometimes in combination with cell blocks, have been the sole preparation technique for these samples. Likewise, the Papanicolaou (Pap) test, by far the most successful screening test for any cancer, was until approximately 10 years ago prepared exclusively as a smear.The screening of Pap smears by humans is a laborious process and is fraught with an irreducible false-negative rate, in part because of inconsistencies in screening performance. With the availability of increasingly powerful computers used for advanced industrial imaging over the past 50 years, several groups have attempted to try to find a way for computers to analyze Pap smears more effectively and more cheaply than human beings can. This proved much more difficult than anticipated. It eventually became clear that the traditional smear was not well suited for analysis by computer. Unlike the human brain, the computer was not well equipped to handle overlapping cells and obscuring background material. Cytyc Corporation was formed in 1987 and successfully developed a liquid-based preparation technique, ThinPrep, which provided wellspaced, primarily single cells against a clean background within a defined, limited area on the slide without air-drying artifact. 3 It became clear that humans found the new preparations easier to read and achieved better screening results with the liquid-based preparation compared with traditional smears. 4 At that point, the company decided to focus on developing and marketing ThinPrep as a new and improved preparation technique to be used for the traditional human examination of slides by light microscopy. Computer-assisted examination of the slides was put on the backburner and would come later. Additional liquid-based cytology (LBC) technologies have followed and currently are available on the market. Studies of thyroid fine-needle aspiration (FNA) using LBC have been based mainly on ThinPrep.ThinPrep was first approved in1991 by the U.S. Food and Drug Administration (FDA) for use in nongynecologic cytologic samples, including FNA samples. ThinPrep was determined to be equivalent to existing specimen preparation techniques such as Cytospin and Millipore, which already were in widespread use for nongynecologic Address for reprints: Britt-Marie Ljung, MD,

Reclassifying Formerly Indeterminate Thyroid FNAs Using the Bethesda System Reduces the Number of Inconclusive Cases

“…From this point on, liquid-based preparations (LBP) will be an alternative method. It is well known that LBP smears improve the quality of cytomorphology, devoid of obscuring elements, and preserve cells adequately [29]. A large-scale study evaluated the efficacy of thyroid FNA compared to LBP with conventional smears and confirmed the effectiveness of LBP for preoperative selection of thyroid neoplasms and decreasing indeterminate diagnoses [30].…”

Performance Differences Between Conventional Smears and Liquid-Based Preparations of Thyroid Fine-Needle Aspiration Samples: Analysis of 47 076 Responses in the College of American Pathologists Interlaboratory Comparison Program in Non-Gynecologic Cytology

“…2 The low diagnostic accuracy of benign lesions on direct conventional smears has not commonly been observed in other studies. Amrikachi et al 13 found that only 3% of cases diagnosed as follicular neoplasms on FNA smears proved to be benign adenomatous nodules.…”

Five Top Stories in Cytopathology

“…126 A recent nationwide educational survey by the College of American Pathologists found a troubling approximately 40% of circulated FNA slides felt to represent FNs were miscategorized as either benign or malignant. 127 An overall 18% diagnostic discordance was found on review of thyroid FNAs referred to a tertiary care center.…”