The impact of using defined criteria for adequacy of fine needle aspiration cytology of the thyroid in routine practice

Abstract

The fine needle aspiration cytology (FNAC) of the thyroid is the predominant method of preoperative tissue diagnosis of thyroid lesions. The routine use of FNAC has reduced the rate of unnecessary surgery for thyroid nodules. However, there are overlaps in the existing criteria for defining adequacy in thyroid aspirates. In this study, we aimed to explore the reasons for high percentage of inadequate thyroid FNAC samples and to reevaluate those samples by applying clearly defined criteria suggested in the literature to reduce the proportion of inadequate aspirates. The results of 550 smears reported as inadequate FNAC samples are presented over a period of 15 years extending from 1986 to 2000 (18.8%). For the purpose of the study, only those patients with subsequent histological or cytological analysis were included (279). The original FNA samples were reviewed by two cytopathologists, unaware of the subsequent repeat cytology or histology results. Specific criteria for adequacy of specimens were used which include the presence of six or more groups of follicular cells, each having more than 10 discernable viable cells or 60 isolated viable follicular cells. Out of 279, 82 (29%) FNAC samples originally reported as inadequate met our criteria and were considered adequate on review. Of these 82 cases, subsequent surgical excision showed malignancy in 5 cases (6%), adenoma in 7 (9%), and benign hyperplasia and thyroiditis in 70 cases (85%). In addition, 16 (5%) cases were classified as cysts. The slide preparation error was noticed in 26 (14%) and the sampling error was observed in 160 (86%) cases. The use of well-defined criteria for adequacy is helpful because it improves the diagnostic efficiency of thyroid FNA and avoids unnecessary surgery for benign nonneoplastic thyroid lesions. However, since application of these criteria has also resulted in an increase in the false-negative diagnoses, they should be applied in the multidisciplinary context.

The Bethesda System for Reporting Thyroid Cytopathology : A Five-Year Retrospective Review of One Center Experience

“…(28) The use of these well-defined criteria for adequacy is helpful because they improve the diagnostic efficiency of thyroid FNA and avoid unnecessary surgery for benign non neoplastic thyroid lesions. (30) The most common pitfalls for false-negative diagnoses in FNA thyroid aspirates reported by Bakhos et al consisted of suboptimal material and under diagnosis of papillary carcinoma due to cystic degeneration with a false-negative rate of 4%. (31,32) Raab et al (33) have also emphasized that suboptimal specimens can be a significant source of false negatives in thyroid cytology.…”

Liquid-Based Cytology in Fine-Needle Aspiration Biopsies of the Thyroid Gland

“…A slide is nonrepresentative when the cellularity does not represent the true components of the lesion (e.g. insufficient amount of follicular cells) [23]. In the first instance the inadequacy of the sampling could be attributed to an incorrect technique, and in the latter the characteristics of the lesion do not allow a definitive cytologic diagnosis [24,25,26].…”

The Accuracy of Fine Needle Aspiration on Superficial Palpable Body Masses in Patients at Tikrit City

“…Results were categorized as "inadequate", when the cellular materials were insufficient for evaluation. Inadequate or unsatisfactory results were reported when the cellular clusters were insufficient for assessment, adequate aspirate is controversial and several reports recommend identification of at least six cellular clusters each having more than 10 discernible viable cells also one should depend on noncellular features such as the confidence and experience of the cytopathologist performing the FNA with regard to needle placement, resistance of the mass to the needle, and correlation with history and physical findings to determine whether the material obtained is truly representative and adequate [10,11].…”

“…The NPV was calculated by using all benign FNA results whether or not further histologic tissue biopsy was taken. Sensitivity=a/(a+c) × 100, specificity=d/(d+b) × 100, PPV=a/(a+b), NPV=d/(d+c) × 100 and the diagnostic accuracy=(a+d/a+b+c+d) × 100 (10). A p-value of <0.05 was considered statistically significant using data analysis tool bar Microsoft Excel.…”