The atypia of undetermined significance/follicular lesion of undetermined significance:malignant ratio

Abstract

BACKGROUND:The Bethesda System (TBS) for reporting thyroid cytopathology introduced the atypia of undetermined significance/follicular lesion of undetermined significance (AUS) category, but did not provide adequate guidance for the appropriate use of this diagnosis. In the current study, the authors sought to identify an appropriate measure for AUS use based on experience to date with TBS.METHODS:The authors reviewed 8 series, including their own laboratory experiences, with a total of 30,466 thyroid aspirates classified within TBS.RESULTS:The median AUS rate was 9.9% with a range of 3.0% to 18.0%. Use of the individual diagnostic categories within TBS varied up to 12.7‐fold. The ratio of “suspicious for follicular neoplasm” plus “suspicious for malignancy” to “malignant” (M) diagnoses varied the least (1.8‐fold). The AUS:M ratio provided a suitable measure of assessing AUS use, with a median ratio of 2.0 and a range of 0.5 to 4.9.CONCLUSIONS:Based on available studies, an AUS:M ratio of 1.0 to 3.0 is recommended. AUS:M ratios > 3.0 are likely because of overdiagnosis of AUS or underdiagnosis of M. AUS:M ratios < 1.0 are mostly due to low AUS rates, at the likely expense of sensitivity. Cancer (Cancer Cytopathol) 2012;. © 2011 American Cancer Society.

Cytotechnologist Performance for Detecting Nuclear Atypia in Indeterminate Thyroid Fine Needle Aspirates

“…This is because the parallels between indeterminate diagnoses in gynecological cytopathology and thyroid cytopathology are few and tenuous. For example, the ASC/SIL ratio that is useful in gynecological cytopathology is difficult to modify for the thyroid, even though some attempts have been made [20]. One of the key differences between gynecological and thyroid malignancy is the diversity of cell types and disease processes in the thyroid.…”

Repeat Fine-Needle Aspiration Biopsy within a Short Interval Does Not Increase the Atypical Cytologic Results for Thyroid Nodules with Previously Nondiagnostic Results

“…The Bethesda System cytopathologic description of the AUS/FLUS category consists of 9 different criteria including the heterogeneous histology results with a wide range of risk of malignancy [1,10,11,12,13,14]. Several studies have attempted to divide the AUS/FLUS category into the subcategories AUS and FLUS [10,11,12,13,14]. Recently, Choi et al [21 ]reported that the AUS subcategory displayed a higher risk of malignancy when using core-needle biopsy specimens.…”

“…According to the Bethesda System for Reporting Thyroid Cytopathology, the category follicular lesion of undetermined significance (FLUS)/atypia with undetermined significance (AUS) includes cases which do not have convincing evidence of benignity or sufficient features in order to conclude that they are follicular neoplasms or suspicious for malignancy [1]. Recently, several studies have attempted to subclassify the AUS/FLUS category into cases with AUS and cases with FLUS [10,11,12,13,14]. AUS refers to a true nuclear atypia with a higher risk of papillary thyroid cancer.…”

The Frequency of ‘Atypia of Undetermined Significance’ Interpretations for Thyroid Fine-Needle Aspirations Is Negatively Correlated with Histologically Proven Malignant Outcomes

“…In TBSRTC, a target utilization rate for the AUS category was set at approximately 7% of thyroid aspirates, a figure based on the observed AUS rates from two large studies published around the time of the 2007 NCI conference [3,4], although it was acknowledged that this figure might be revisited. To date, the majority of laboratories that have retrospectively examined their experience with AUS in TBSRTC framework report rates higher than the 7% target, with a range of 2.1–18% [5,6,7,8,9,10,11,12,13,14,15]. It is not well understood what factors contribute to this variable usage by cytopathologists.…”