Cytomorphologic significance of marginal vacuoles in diffuse thyroid enlargements

BACKGROUND: Fine needle aspiration cytology (FNAC) of the thyroid is an established first-line test for thyroid lesions. Marginal vacuoles (MVs) have been associated with hyperactivity of the thyroid, but some studies have pointed towards their nonspecific status. AIMS: To assess the presence of MVs in diffuse thyroid enlargements and evaluate the strength of correlation between MVs, levels of thyroid hormone and cytological diagnosis. MATERIALS AND METHODS: Ninety-seven cases of diffuse thyromegaly were studied. Cytomorphological features were examined with special attention to MVs. MVs were graded as scant, moderate and abundant. Hormonal status of the patients was recorded. The presence and grading of MVs was correlated with cytological diagnosis and hormonal status. The strength of association was studied by applying the Chi-square test and test of proportion; a P ≤ 0.05 was considered significant. RESULTS: Abundant MVs were not associated with hypothyroidism in this study; 79% of these cases were hyperthyroid. The correlation between moderate/insignificant MVs and functional status of the thyroid gland was inconclusive. Further, abundant MVs in thyroid FNACs were seen in cases of primary hyperplasia and Hashimoto's thyroiditis. There was a significant correlation between the presence of abundant/moderate MVs and primary hyperplasia and their absence in colloid goiter (P = 0.01 and 0.004, respectively). CONCLUSIONS: A significant association was found between abundant MVs and a hyperthyroid state. Moderate/absent MVs in diffuse goiters were not found to correlate with thyroid function. Thus, all diffuse goiters with prominent MVs require hormonal evaluation to rule out hyperfunction of the thyroid.