Accuracy of different cytoarchitectural features in the diagnosis of papillary thyroid carcinoma by fine needle aspiration

Fine needle aspiration (FNA) has about 90% diagnostic accuracy for papillary thyroid carcinoma (PTC) in an adequate sample. Ignorance of relative significance of individual cytologic features may lead to misdiagnosis due to reliance on a single or few features. Our objective was to determine the usefulness of individual and most appropriate combined cytologic features, for diagnosis of PTC. H&E stained FNA smears of fifty cases each, of consecutive histologically confirmed PTC and benign thyroid cases (controls), reported over 3 years, were retrieved from the files. A total of 31 architectural, cytological and background features were assessed, blind to the final diagnosis and compared amongst the two groups. The statistical significance (p<0.05) of each parameter was determined by chi-square and odds ratio and combinations quality assessed by ROC curves.: Twenty features were found to be statistically significant. Fourteen highly significant (p<0.000) features included flat syncytial sheets, anatomical borders, true papillae, cellular swirls, individually dispersed cells with eosinophilic cytoplasm, anisonucleosis, elongated oval nuclei, powdery chromatin, nuclear outline irregularity, thickened nuclear membranes, crescent shaped nuclei, intranuclear inclusions, histocytoid cells and soap bubble cytoplasmic vacuolation. The six statistically significant features (p<0.05) included micro-acinar structures, cellular crowding, nuclear overlapping, nuclear grooves, squamoid cells and bubble gum colloid. The control group also showed some of these single cytologic features. All the combinations of ≥ 4 features had a statistical significance of p=0.000 and specificity and PPV of 100% with ROC showing excellent results. Using correct combination of cytologic features will increase accuracy of FNA diagnosis of PTC.