Marginal vacuoles in thyroid aspirates.
To report on two cases of metastatic follicular carcinoma with marginal vacuoles (MVs) and review smear results in 441 solitary nodular goiters (SNGs) for this cytologic feature. The first case was a 55-year-old male who presented with a huge mass in the left hip region; the second case was a 50-year-old male with a thyroid nodule and a large mass on the scalp. The age of the 441 ultrasonographically diagnosed SNG cases ranged from 11 to 75 years. The May-Grünwald-Giemsa-stained fine needle aspiration (FNA) smears of these cases were reviewed by one of the authors (D.K.D.) for various cytomorphologic features, including MVs. FNA smears from the mass in the hip in the first case showed follicular cells with acinar formation and MVs, indicating metastatic follicular thyroid carcinoma (FTC). These features were of help in detecting the thyroid primary, which had previously gone undetected. Aspiration smears from the thyroid nodule and the mass on the scalp in the second case showed tumor cells of FTC with MVs and microfilariae. Review of 441 SNG cases revealed MVs in 42.6% of hyperplastic nodules; that rate was significantly higher (P < .001) than that of colloid goiter (5.2%) and neoplastic goiter (13.3%) but lower (P < .05) than that of thyrotoxic goiter (100%). MVs were limited to neoplasms with a follicular component; that included 15% of follicular neoplasms and 50% of follicular variant of papillary carcinoma (FVPC). The difference between FVPC and the rest of the neoplastic goiters (6%) was statistically significant (P = .002).