Isolated macrocalcifications were initially described as a benign ultrasonographic (US) pattern of a thyroid nodule in the French Thyroid Imaging Reporting and Data System [1] and defined as macrocalcifications with no solid component or vascular signal [2]. Subsequently, recent studies [3,4] have demonstrated that isolated macrocalcifications have an intermediate malignancy risk, are mostly found in papillary carcinomas, and that malignant tumors with isolated macrocalcifications may show aggressive behavior, such as advanced local invasion or macroscopic cervical lymph node metastasis.

We agree that the term "isolated macrocalcification" may not be intuitive for "a calcified nodule with posterior acoustic shadowing in which any soft tissue component is not identified due to the dense posterior acoustic shadowing on US." Furthermore, we concur that the suggested terms ("totally calcified nodule" or "macrocalcified nodule without a solid component") are simple and more intuitive for understanding the US characteristics of isolated macrocalcifications. However, we need more consensus on the appropriate descriptors for US patterns of calcified nodules, and we therefore hope that a standardized terminology of isolated macrocalcifications will be established through the ongoing International Thyroid Nodule Ultrasound Working Group, in which the majority of professional thyroid societies are involved, including the Korean Society of Thyroid Radiology (KSThR).

A previous study [3] reported that small thyroid cancers with isolated macrocalcifications may show the aggressive behavior of macroscopic lymph node metastasis. Therefore, even though the KSThR guideline currently recommends biopsy for isolated macrocalcifications only when the nodule size is equal to or larger than 1 cm, US monitoring of small isolated macrocalcifications may be necessary. Although our study revealed that the majority of isolated macrocalcifications are composed of coarse central calcifications [5], the histopathologic features of isolated macrocalcifications have only been investigated to a limited extent. We agree that the investigation of histopathologic features using core-needle biopsy specimen would be useful for identifying the characteristics of benign and malignant isolated macrocalcifications, which will be another step towards understanding the nature of isolated macrocalcifications in the thyroid gland.