Pitfalls in cytological diagnosis of autoimmune thyroiditis

The aims of this study are to document pitfalls in cytologic diagnosis of a utoimmune thyroiditis (AT) and highlight possible ways to minimize them. On e hundred consecutive thyroid aspirates with features diagnostic or suggest ive of AT, performed and reported by the first author, were included in the study. Follow-up was traced and cytologic features responsible for indecis iveness were re-assessed in those reported as suggestive of AT. The feature s were then correlated with the results of serologic and thyroid function t ests and clinical features, and an attempt was made to amend the final diag nosis using an integrated approach. Seventy eight were diagnostic and 22 we re suggestive of AT. In the latter 22, features responsible for the indecis iveness were: cytologic atypia, in the form of nuclear enlargement, irregul arity and grooves and altered chromatin texture, in 14 (64%); nucleoli with suspicion of a coexisting neoplasm in three (13.6%), two of which showed e pithelial preponderance, crowding and discohesion; sparse inflammation in f our (18%); a predominant lymphoid population without epithelial cells resem bling a reactive lymphnode in one (4.5%); coexisting toxic features in two (9%); and scanty smears in one (4.5%). Eighteen of the 22 suspected of AT h ad follow-up. Six had been assessed histologically; three with features sus picious of a neoplasm were diagnosed respectively as a papillary carcinoma (PC), Hurthle cell carcinoma (HCC) and a multinodular goitre (MNG) with deg enerate changes. The other three were confirmed as AT; one with cytologic a typia, one with sparse inflammation and the third as cytologically resembli ng a reactive lymphnode. In ten of the remaining 12, the final diagnosis co uld be revised following an integrated approach with possible reduction of the indecisiveness. Potential pitfalls are: cytologic atypia occurring in AT; abundance or scar city of background inflammation; low cell yield; and cc-existing toxicity a nd malignancies. Epithelial preponderance over inflammation, nuclear crowdi ng, severe atypia and cell discohesion should raise the possibility of a ne oplasm in spite of other features of AT. Awareness of possible pitfalls and adopting an integrated approach, especially in difficult situations, will minimize pitfalls.