Factors Influencing Inadequacy in Rapid Onsite Evaluation of Ultrasound Guided Fine Needle Aspiration (FNA) Samples of Thyroid Nodules

Thyroid nodules are a common clinical finding with a prevalence of around 50-67% in the general population using ultrasound examinations. Of these, malignancies account for 5-15% including the treatable papillary and follicular thyroid carcinomas and the rarer but more aggressive medullary and undifferentiated thyroid cancers. Fine Needle Aspiration (FNA) is a relatively simple, cost-effective recommended standard diagnostic procedure with high sensitivity and specificity for the preoperative evaluation of benign and malignant thyroid nodules. Cytopathology reports of thyroid FNA are categorized using a universal grading system, which helps to standardize reporting of diagnostic thyroid cytology results. In the non-diagnostic/unsatisfactory category (Bethesda I), ranging from 1% to 20% of samples, pathologists are unable to make a clinical diagnosis based on these samples due to an inadequate number of cells or difficulty in identifying cells. The estimated risk of malignancy in this category is 1-4 %, which usually managed by repeating FNA with increase in patient discomfort, procedural complications and medical costs. There are few other prospective studies investigated the effect of needle size, and sampling technique on sample adequacy.