Thyroid imaging reporting and data system (TI-RADS)

TIRADS classification system is being advocated similar to BIRADS category for breast lesions. Although not accepted globally, it may help radiologists in classifying and risk stratification of thyroid lesions.

Classification system has been proposed by Horvath et al¹, with a modified recommendation from Jin Kwak et al².

Similar to BIRADS category, sonographic TIRADS classification is as follows-

• TIRADS 1 - normal thyroid gland
• TIRADS 2 - benign lesions
• TIRADS 3 - probably benign lesions 
• TIRADS 4 - suspicious lesions (subclassified as 4a, 4b, and later 4c ² with increasing risk of malignancy)
• TIRADS 5 - probably malignant lesions (more than 80% risk of malignancy)
• TIRADS 6 - biopsy proven malignancy

TIRADS 2 category

• avascular anechoic lesion with echogenic specks (colloid type I)
• vascular heteroechoic non-expansile, non-encapsulated nodules with peripheral halo (colloid type II)
• isoechoic or heteroechoic, non-encapsulated, expansile vascular nodules (colloid type III)

These conditions have 0% risk of malignancy.

TIRADS 3 category

• hyperechoic, iso-echoic or hypoechoic nodules, with partially formed capsule and peripheral vascularity, usually in setting of Hashimoto's thyroiditis (Hashimoto's pseudonodule)

Modified TIRADS classification² have simplified TIRADS 3 category as none of the suspicious malignant sonographic features described below. These lesions are mostly benign with <5% risk of malignancy¹.

TIRADS 4 and 5 categories

These categories are based on five suspicuous sonographic features of malignancy

1. solid component
2. markedly hypoechoic nodule
3. microlobulations or irregular margins
4. microcalcifications
5. taller-than-wider shape

• TIRADS 4a - one suspicious feature
• TIRADS 4b - two suspicious features
• TIRADS 4c - 3-4 suspicious features
• TIRADS 5 - all five suspicious features

TIRADS 4a has 5-10% risk of malignancy, 4b and 4c may have 10-80% risk of malignancy. TIRADS 5 category lesion have >80% risk of malignancy¹.

See also

• BIRADS classification system

Disclaimer: At the time of writing this article, this classification system in any version has not been formally accepted by ACR or any global radiological convention. Yet this classification system is well reported. Article is based on proposed classification systems, which should be known to the radiologists, and may help them in characterizing thyroid lesions . It may be used for risk stratification on sole discretion of personnel or institution, and should be complemented by FNAC on need basis.