Follicular lesions of the thyroid: intraoperative cytology

The aim of this study is to evaluate the role and utility of intraoperative cytology in differentiating between follicular adenomas and non-neoplastic adenomatous nodules of the thyroid. We retrospectively reviewed the intraoperative cytologies of 36 adenomatous nodules and 19 follicular adenomas and evaluated several features. chi-square statistics were used to determine a statistically significant difference in cytologic scores between the two groups. We found significant differences in grading scores of the following parameters: follicular adenomas showed greater cellularity, greater follicle formation, larger nuclei, and more nuclear pleomorphism and overlap; adenomatous nodules showed more colloid and honeycomb arrangements. However, inspection of the data in graphic form showed a partial overlap in cytological features between the two groups: an adenomatous nodule revealing a microfollicular pattern histologically will cytologically display numerous follicles and scant colloid, giving a false impression of a neoplasm; while the smear of a macrofollicular adenoma is relatively hypocellular and contains abundant colloid, causing potential misdiagnosis as an adenomatous nodule. In conclusion, intraoperative cytologic examination can help to detect those follicular lesions more likely to be neoplastic, and a systematic approach is proposed when dealing with thyroid follicular lesions during intraoperative consultation in order to improve the diagnostic accuracy.