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Ultrasonographic guideline for thyroid nodules cytology: single institute experience

Purpose The main issue with the current ultrasonography (US) guidelines is the overestimation of malignant and indeterminate nodules as they do not aid in making decisions to treat patients. To overcome this, new US guidelines for thyroid nodules that have been shown to be better correlated with cytologic results have been proposed. We also suggested specific indications for US-guided fine needle aspiration (FNA) using the new US guidelines. Methods Clinical and pathologic data from 925 patients and 1,419 thyroid nodules were retrospectively collected. All subjects underwent US- and US-guided FNA at Department of Surgery, Wonju Christian Hospital, between March 2010 and July 2011. Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were calculated for both the current guidelines and the new guidelines. Results The accuracy, sensitivity, specificity, PPV, and NPV for the current guidelines in predicting malignancy were 24.1%, 99.3%, 62.2%, 25.0%, and 99.8%, respectively. The accuracy, sensitivity, specificity, PPV, and NPV for the new guidelines in predicting malignancy were 66.0%, 96.0%, 86.7%, 47.7%, and 99.4%, respectively. Conclusion The use of the new US guidelines allow for a more accurate and specific diagnosis and a better treatment plan than the current guidelines. Additionally, the use of the new FNA guidelines may help prevent unnecessary FNAs and promote cost-effective follow-up for patients.


INTRODUCTION
Approximately 4% to 7% of all adults have thyroid nodules. Current epidemiologic data have shown that only 5% to 6.5% of the reported cases of thyroid nodules found by ultrasonography (US) are malignant and require further workup [1][2][3]. As the increasing prevalence of thyroid cancer increases, there is a need for a method that can identify malignant lesions that warrant further surgical treatment [4,5].
To date, fine needle aspiration (FNA) is not only the traditional diagnostic test for identifying malignant thyroid nodules [6], but also represents the "gold standard" preoperative test for diagnosing thyroid cancer. However, the sensitivity of FNA ranges from 65% to 98%, and the specificity from 72% to 98% [7]. The Bethesda classification system is typically used for indeterminate cytological results (atypical cells of undetermined significance, follicular nethesurgery.or.kr oplasm or suspicion of follicular neoplasm, suspicion of malignancy), which can further complicate the situation.
Consequently, surgical resection is often required in indeterminate cases for a definitive diagnosis. Therefore, a comprehensive diagnostic algorithm using US findings is of interest to ensure accurate diagnosis and therapeutic planning, and to decrease diagnostic operative resections.
Neck US has long been used to evaluate the size, character and location of thyroid nodules, monitor nodule growth, and identify locoregional lymphadenopathy [6,[8][9][10]. Many studies have classified specific US characteristics predictive of malignant thyroid nodules. For instance, current US characteristics are that strongly correlated with malignancy include increased intranodular vascularity, the presence of micro-of macrocalcifications, a taller-than-wide pattern, hypoechogenecity, and speculated margins [11,12]. Although controversial, the current guidelines state that if any one of the above findings is observed, with the exception of increased intranodular vascularity, the nodule should be defined as suspicious for malignancy. In contrast, simple cysts defined as nodules that are predominantly cystic, cystic with comet tail artifacts, or nodules with a spongiform appearance are all likely to be benign. Indeterminate nodules are those that are not characteristic of either malignant or benign [11,13].
As the main issue with the current guidelines is the overestimation of malignant and indeterminate nodules, they are not useful in the decision-making process of a treatment plan as they result in unnecessary invasive procedures, including FNA and diagnostic thyroidectomy.
The purpose of this study is to address the disadvantages of the current guidelines by suggesting a new US-based guideline system for thyroid nodules. As well, with the use of these new guidelines, we discuss specific indications for US-guided FNA.

METHODS
Clinical and pathologic data were retrospectively col-      Cooper et al. [17] reported that with the exception of suspicious cervical lymphadenopathy, a specific but insensitive However, this classification system is difficult to apply clinically due to its marked complexity [19]. Therefore, the intention to develop a more accurate, and simple guideline for thyroid nodules was explored.
Frates et al. [14] reported a range of sensitivity, specificity, PPV, and NPV of US characteristics suggested for malignancy by current guideline.
Sensitivity, specificity, PPV, and NPV of US characteristics suggesting malignancy by the current guidelines in this study was similar to that. Especially, sensitivity of marked hypoechogenecity is the highest. Generally, the new guidelines had better specificity and PPV than the current guidelines. Even though the current guidelines were more sensitive than the new guidelines. It seems to be the cause of lower sensitivity of the new guidelines than the current guidelines.
The results showed that the new guidelines had better accuracy, specificity, and PPV than the current guidelines, although the NPV was not significantly different between the two. Even though the current guideline system was more sensitive than the new guidelines, the new guidelines allowed for better diagnostic accuracy and proper   well-defined, taller-than-wide, and isoechoic with peripheral hypoechoic halos (Fig. 1), and three cases where the lesions were well-defined, oval-shaped, and markedly hypoechoic (Fig. 2). Together, these six nodules were diag- we recommend the lesion be followed by US (Fig. 3). These new FNA guidelines help avoid unnecessary FNAs and promote a cost-effective follow-up for patients.
In conclusion, the use of the new US guidelines allow for greater accuracy with higher specificity for diagnosis and treatment planning than the current guidelines.
Additionally, the use of the new FNA guidelines based on the new US guidelines help avoid unnecessary FNAs and promotes cost-effective follow-up for patients.

CONFLICTS OF INTEREST
No potential conflict of interest relevant to this article was reported.