Value of measurement of nuclear diameter of cells in fine needle aspiration smears in the diagnosis of follicular lesions of the thyroid

Introduction: Subjective assessment of thyroid epithelial cells in aspiration cytology smears is often not useful in distinguishing benign and malignant thyroid follicular lesions.

Objectives: To determine whether objective measurement of the nuclear diameter of thyroid follicular epithelial cells in smears would be useful in distinguishing benign and malignant thyroid follicular lesions. 

Method: Fine needle aspiration cytology of histologically proven follicular adenoma (FA, n=50), hyperplastic nodule (HN, n=38) and follicular carcinoma (FC, n=24) stained with Papanicolaou stain and haematoxylin and eosin stain were assessed. The “cellSens” computer software (Version 1.16) was used with an Olympus BX53 microscope for the measurement of nuclear diameters. The nuclear diameters of 100 cells (x400 magnification) were measured from each case and the mean and standard deviation were calculated. Statistical analysis was carried out with a two-sample pooled t-test and one-way ANOVA test with post hoc testing.

Results: The two-sampled pooled t-test showed that there was no significant difference in nuclear diameters between the two stains (p>0.25). The one-way ANOVA test showed that there was a significant difference between the mean nuclear diameters of these three groups (p<0.001). The post hoc test showed that there was a significant difference between FA versus FC and HN versus FC (p<0.001). A significant difference was also seen between FA and HN (p<0.05). The 95% confidence intervals (CI) showed that FC had a distinct range of nuclear diameters which were higher than FA and HN. However, the 95% CI values for FA and HN showed an overlapping grey area.

Conclusion: Objective measurement of nuclear diameter in thyroid cytology smears may prove to be useful in distinguishing benign follicular lesions from malignant follicular lesions.