5 Syed Z. Ali and Edmund S. Cibas (eds.), The Bethesda System for Reporting Thyroid Cytopathology, DOI 10.1007/ 978-0-387-87666-5_2, © Springer Science+Business Media, LLC 2010 Chapter 2 Nondiagnostic/Unsatisfactory Barbara A. Crothers, Michael R. Henry, Pinar Firat, and Ulrike M. Hamper Background In order to provide useful diagnostic information for optimal clinical management, a fine needle aspiration (FNA) sample of a thyroid nodule should be represen- tative of the underlying lesion. A good criterion of adequacy, when appropri- ately applied, ensures a low false-negative rate. It is worth emphasizing, however, that cellularity/adequacy is dependent not only on the technique of the aspirator, but also on the inherent nature of the lesion (e.g., solid vs. cystic). In general, the adequacy of a thyroid FNA is defined by both the quantity and quality of the cellular and colloid components. An assessment of specimen adequacy is an integral component of an FNA interpretation because it conveys the degree of certainty with which one can rely on the result. The definition of an adequate specimen in thyroid FNA is subjective and controversial. While the quality of a specimen is irrefutably critical to proper interpretation, controversy is introduced when rigid numer- ical criteria for cell quantity are imposed. No study supports any specific follicular cellularity as applicable to all cases (benign and malignant, cystic and solid) with high diagnostic accuracy. Additionally, there is no consensus supporting a minimum number of FNA passes required to obtain adequate samples. High quality specimens contain sufficient cells representative of a lesion to allow the observer to confidently render an accurate interpretation. High quality requires proficient collection combined with excellent slide preparation, processing, and staining. Historically, the terms “nondiagnostic” and “inadequate/unsatisfactory” have been used interchangeably by some but not all cytopathologists: some cytopathologists (and endocrinologists) have interpreted the terms to mean different things. 1 An unsatisfactory specimen is always nondiagnostic, but some technically satisfactory specimens may also be considered “nondiag- nostic,” that is, showing nonspecific features not conclusively diagnostic of a particular entity. At the NCI conference, the terms “Nondiagnostic (ND)”