Thyroid imaging reporting and data system (TI-RADS)

TIRADS is a risk stratification system for classifying thyroid lesions and was recently recognized in an ACR white paper ⁵. Its use is being advocated similar to BIRADS category for breast lesions. 

Classification system has been proposed by Horvath et al¹, with a modified recommendation from Jin Kwak et ala ².

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

• TIRADS 1: - normal normal thyroid gland
• TIRADS 2 - benign: 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 suspicuoussuspicious sonographic features of malignancy:

• solid componen-it means component
  • high stiffness of nodule on elastography if available
• markedly hypoechoic nodule
• microlobulations or irregular margins
• microcalcifications
• taller-than-wider shape

Subclassificaiton

• TIRADS 4a- one: one suspicious feature
• TIRADS 4b- two: two suspicious features
• TIRADS 4c- 3-4: three/four 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

DisclaimerPlease note: 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.