Impact of the Reclassification of the Non-Invasive Follicular Variant of Papillary Carcinoma as Benign on the Malignancy Risk of the Bethesda System for Reporting Thyroid Cytopathology: A Meta-Analysis Study.

OBJECTIVES

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) established diagnostic categories for cytologic specimens of the thyroid. Each category was associated with an estimated risk of malignancy. Recently, the non-invasive follicular variant of papillary thyroid carcinoma has been reclassified as benign. This reclassification may alter the malignancy risk of TBSRTC diagnostic categories.

STUDY DESIGN

A literature search was made for all studies investigating the effect of reclassification of some non-invasive follicular variant papillary thyroid carcinomas as benign on the malignancy risk associated with TBSRTC categories. The authors calculated the malignancy risk for TBSRTC categories in a series of 315 thyroid aspirates when the non-invasive follicular variant of papillary thyroid carcinoma was considered benign. A meta-analysis of malignancy risk data for the 3 published studies and the current study was performed.

RESULTS

The meta-analysis showed that the malignancy risk was reduced for all TBSRTC categories except the "non-diagnostic" category. The reduction in malignancy risk was greatest in the categories "suspicious for malignancy" and "atypia/follicular lesion of undetermined significance."

CONCLUSION

A meta-analysis of all pertinent studies demonstrated that re-categorization of the non-invasive follicular variant of papillary thyroid carcinoma as benign reduces the malignancy risk in the majority of TBSRTC categories.