Comment on “Partially Cystic Thyroid Nodules on Ultrasound: Probability of Malignancy and Sonographic Differentiation”

Dear Editor:

We read with great interest the article by Lee et al., “Partially Cystic Thyroid Nodules on Ultrasound: Probability of Malignancy and Sonographic Differentiation” (1), which appeared in the Volume 19, Number 4, issue of Thyroid.

In that retrospective study, the authors concluded based on their data set that in partially cystic thyroid nodules, when >50% of the nodule is solid or the solid portion of the nodule is eccentric, the risk of malignancy is greater.

However, the paper simply used univariate analysis for the delineation of ultrasound (US) features significantly associated with malignancy, ignoring the inherent correlation between the suspicious US features of partially cystic thyroid nodules. As mentioned by Na et al. (2), only microcalcification was independently predictive of malignancy in the partially cystic nodule group. Although the US feature of eccentric configuration with an acute angle was associated with malignancy in partially cystic nodules, it was less sensitive for malignancy compared with microcalcification.

To analyze the correlation between the two suspicious US features—the solid portion ≥50% and the solid portion of the nodule is eccentric—the raw data reported in the presented contingency table in the original manuscript was recalculated (Table 1). The stratified analysis was used for data analysis. Patients were regrouped, and in the solid portion ≥50% group, an eccentric solid portion showed a statistically significant association with a malignant partially cystic thyroid nodule (p = 0.001). Conversely, no significant difference was found in the solid portion <50% group (p = 0.085).

Thus, we come to the conclusion that only in the solid portion ≥50% nodules is eccentric positioning of the solid component significantly associated with malignancy, but it cannot be regarded as a predictor of malignancy in the partially cystic thyroid nodules. Because of the limited cases studied, further investigations with a large series of non-solid nodules are needed to determine the predictability of US features.