Follicular neoplasms with nuclear atypia versus other types of atypia: Should follicular neoplasms be stratified according to the presence of nuclear atypia?

The third edition of The Bethesda System (TBS) subclassifies the atypia of undetermined significance (AUS) category on the basis of the presence of nuclear atypia (AUS-Nuclear). This approach is supported by studies showing significant differences in the risk of malignancy (ROM) between AUS-Nuclear and those without (AUS-Other). Although aspirates of follicular neoplasms (FNs) are characterized by marked architectural atypia, TBS recognizes the infrequent occurrence of FNs with mild nuclear atypia (FN-Nuclear). Furthermore, limited studies have shown significant differences in ROM between FN-Nuclear and those without (FN-Other). This study explored potential differences in ROM, molecular-derived risk of malignancy (MDROM), and molecular alterations between FN-Nuclear and FN-Other.