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

Overview

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.

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. The American Thyroid Association has devised an algorithm "Thyroid Imaging Reporting and Data System (TI-RADS) for evaluation and management of thyroid nodules based on US pattern and size to recommend fine needle aspiration (FNA) cytology to minimize unnecessary FNAs/thyroid surgeries for nodules that are most likely benign and to avoid over-treating micropapillary thyroid carcinoma which is indolent. 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 called The Bethesda System for Reporting Thyroid Cytopathology, which helps to standardize reporting of diagnostic thyroid cytology results \[3\]. 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. Several retrospective and prospective studies investigated the factors associated with non-diagnostic samples rates, most of which focused on ultrasound guidance, the rapid on-site cytological evaluation and cystic components of the nodule. However, there are few other prospective studies investigated the other nodule characteristics, needle size, and sampling technique.