Subclassification of Follicular Neoplasms Recommended by the Japan Thyroid Association Reporting System of Thyroid Cytology

Table 1

Cytological reporting system recommended by the Japan Thyroid Association guidelines for clinical practice on the management of thyroid nodules, 2013.

Diagnostic category	Risk of malignancy
① Inadequate (nondiagnostic)	10%
② Normal or benign	<1%
③ Indeterminate
(A) Follicular neoplasms (follicular pattern lesions)
(A-1) Favor benign	5–15%
(A-2) Borderline	15–30%
(A-3) Favor malignant	40–60%
(B) Others	40–60%
④ Malignancy suspected (not conclusive for malignancy)	>80%
⑤ Malignancy	>99%