Comparison of risk of malignancy in a subgroup with atypia of undetermined significance/follicular lesion of undetermined significance: A meta-analysis

Background: As heterogeneous findings are included in the atypia of undetermined significance (AUS)/follicular lesion of undetermined significance (FLUS) category, differing risks of malignancy in subgroups have been reported in several articles. Methods: We performed a meta-analysis of full-text publications written in English found in the Embase and PubMed databases. Results: The 4-tiered subgroup proportion meta-analysis showed that the 95% confidence interval (95% CI) of the risk of malignancy in the cellular atypia group did not overlap with the other 3 subgroups and demonstrated a significant difference. Two-tiered analysis using the cytologic and architectural atypia groups showed that cytologic atypia group had a 2.64-fold increase in the risk of malignancy compared with the architectural atypia group. Conclusion: The cytologic atypia had a significantly higher risk of malignancy than the architectural atypia group, and it should be considered as a separate category.