Intranuclear cytoplasmic inclusions (invaginations) in thyroid aspirations. Frequency and specificity.

In order to determine the frequency and specificity of intranuclear cytoplasmic inclusions (invaginations), described by some as an important criterion for the cytologic diagnosis of thyroid carcinoma, 258 consecutive thyroid aspirates were reviewed. Intranuclear cytoplasmic inclusions were present in 91% of the papillary adenocarcinomas but were not seen in any of the benign thyroid lesions or in any of the few nonpapillary adenocarcinomas in the study. It is concluded that the presence of intranuclear cytoplasmic inclusions in thyroid aspirates is probably specific to thyroid carcinoma but is not necessarily restricted to the papillary variant.