Cytomorphological Differences between Liquid-Based Cytology and Conventional Smears in Fine-Needle Aspirates of Thyroid Lesions

BACKGROUND: Liquid-based cytology (LBC) is becoming an independent processing modality for cytology specimens. Decreased obscuration, single-slide examination, lesser screening time, and potential application of ancillary techniques are the various advantages it offers. AIM: To study and compare the cytological features of fine-needle aspirates from thyroid swellings on LBC with conventional smears (CS). MATERIALS AND METHODS: Fine-needle aspiration was performed on 150 patients with thyroid nodule. The aspirate was first used to prepare a minimum of two CS and the remaining aspirate was used to prepare one SurePath smear. The final diagnosis was given according to the Bethesda system for reporting thyroid cytopathology (2007). Cytomorphological parameters were semi-quantitatively scored. Pearson's Chi-square test was used and P value was calculated. A P value <0.05 was considered significant. Cytohistological correlation was done wherever possible. RESULTS: LBC showed higher nondiagnostic rate than CS. Significant cytomorphological differences on LBC included: (i) higher frequency of single, naked nuclei; (ii) lesser nuclear and cytoplasmic details; (iii) decreased colloid which appeared differently (as napkin fold and dense droplet); (iv) increased cyst macrophages; and (v) decreased obscuration by blood. CONCLUSION: LBC can supplement CS but cannot replace it.