Comparison of Two Different Methods of Fine Needle Aspiration Biopsy and Histopathology for Thyroid Nodules

Two different methods for fine needle aspiration biopsy (FNAB) of thyroid nodules (multi-pass conventional smear, MPCS; single-pass liquid-based cytology, SPLBC) were evaluated regarding the magnitude of nondiagnostic/unsatisfactory sampling ratio, and basic demographic and ultrasonographic (USG) factors to predict such outcome.

One thousand FNAB patients were retrospectively assessed. Of them, 517 nodules were evaluated with the conventional smear method, and the rest were evaluated with liquid-based cytology method using the Bethesda System for Reporting Thyroid Cytopathology. FNAB technique had certain procedural differences for both pathological methods. For conventional smear, a modified "needle-only" technique with three independent passes was performed, whereas a single pass was used for liquid-based cytology. The reduction of nondiagnostic/unsatisfactory results constituted the basis of this study. Pathological results, therefore, were subgrouped under "nondiagnostic/unsatisfactory" (Category I), "benign" (Category II), and "atypia/neoplasia/malignancy" (Category III-VI).

Both FNAB groups were not statistically different or only slightly different regarding size (P = 0.196), echogenicity (P = 0.014), and the presence of echogenic foci (P = 0.11), therefore considered to have equal USG properties. In MPCS method, the nondiagnostic/unsatisfactory rate (i.e., Category I) was 24%. Other cytological results were as follows: Category II (67.1%), Category III-VI (8.8%). In SPLBC method, the nondiagnostic/unsatisfactory rate (i.e., Category I) was 14.5%. Other cytological results were as follows: Category II (77.6%), Category III-VI (7.8%). A significant difference was found between two sampling methods regarding pathological results (Independent samples t-test, P < 0.0001). The demographic and USG factors, considered in this study, did not offer a successful prediction of nondiagnostic/unsatisfactory outcomes.

SPLBC has significantly lower (14.5% vs 24%) nondiagnostic rate than MPCS, and higher 77.6% vs 67.1%) Category II rate than MPCS. This may point to the possibility that MPCS method undercategorizes many benign (i.e., Category II) nodules under nondiagnostic/unsatisfactory category. The success of the former is due to the elimination of confounding material during the process. Single pass, also, increases patient comfort and compliance, and has additional advantages for the interventionalist, as it obviates the need to smear aspirates. This dramatically decreases the actual duration of the biopsy procedure and is free of interventionalist expertise for smearing.