- TR3 means mildly suspicious and TR4, moderately, and in the multicenter validation, about one in eleven TR4 nodules turned out malignant, and TR3 stayed below one in twenty.
- Size decides what is done: a TR3 is biopsied from 2.5 cm and a TR4 from 1.5 cm, and below that, they are followed.
- When the report asks for no biopsy, what remains is a schedule of ultrasounds, and growth has a precise definition.
The TIRADS is the sum of points the radiologist assigns to five features of the nodule, and the result is grouped into five categories. TR3 is exactly three points, and TR4, between four and six. That single-point difference changes the size from which a biopsy is done and how often the ultrasound is repeated. What follows is the translation of the two categories, and of what comes after each.
What each category says
TR3 means mildly suspicious: a nodule with some feature that adds points, almost always being A nodule made of tissue, with no fluid inside. It is the most frequent type and adds one point to the scale. or somewhat darker than the surrounding tissue, but none of those that weigh most. TR4 means moderately suspicious: it already adds several features, or one of the heavy ones, such as an irregular margin or a bright spot. Neither is a diagnosis. They are a probability, and the probability has been measured.
- 9 %of TR4 nodules turned out malignant in the multicenter validation of the system, with 3,422 nodules with pathology results. With four points, 6 %, and with six, 13 %.Middleton WD et al. AJR Am J Roentgenol. 2017, 208(6): 1331-1341.
- 5 %is the risk ceiling the system sets for TR3, and in that same validation the category stayed around that threshold or below.Tessler FN et al. J Am Coll Radiol. 2017, 14(5): 587-595 · Middleton WD et al. AJR. 2017.
It helps to read it the other way round: nine in ten TR4 nodules are benign, and more than nineteen in twenty TR3 are too. The category does not say there is cancer, and it says how much it is worth looking closer, and from what size.
Why size decides
A small nodule, even a suspicious one, rarely causes harm before a follow-up ultrasound detects it, and that is why the system does not biopsy everything that adds points, but what adds points and is also large enough. These are the thresholds, and they are the ones applied by radiologists using the American College of Radiology system.
TR3, mildly suspicious
- Biopsy if it measures 2.5 cm or more
- Ultrasound follow-up if it measures between 1.5 and 2.5 cm
- Below 1.5 cm, the system does not call for follow-up
- Ultrasound at one, three and five years
TR4, moderately suspicious
- Biopsy if it measures 1.5 cm or more
- Ultrasound follow-up if it measures between 1 and 1.5 cm
- Below 1 cm, it does not need follow-up
- Ultrasound at one, two, three and five years
The thresholds are from the 2017 ACR TI-RADS system. Your radiologist may use another system with different thresholds, and it helps to know which one appears in your report.
When no biopsy is asked for, what remains is a schedule
It is the phrase that reassures most and is misunderstood most. A 1.2 cm TR4 is not biopsied, but it is followed, and followed on a schedule: at one, two, three and five years. What each ultrasound looks for is one thing: whether it grew. And growth has a precise definition, so it does not depend on whether the radiologist measured a millimeter more or less.
That is why having the previous ultrasound matters so much: without it there is nothing to compare against, and the follow-up loses its comparative value.
And if it is biopsied, what comes next
The biopsy does not replace the ultrasound: it complements it. Its result comes in A six-category system the pathologist uses to report a thyroid biopsy result. II is benign, VI is malignant, and III and IV are indeterminate. categories, and the two scales together are what decide.
- 01The punctureUltrasound-guided, in a few minutes, back to routine the same day. Cells are taken from the nodule with a fine needle.
- 02The result, in Bethesda categoriesBenign, indeterminate, suspicious or malignant. Most TR3 and TR4 nodules that are biopsied come back benign.
- 03The decision, with both in handTIRADS and Bethesda together. A TR4 with a benign biopsy is followed, and if it also causes symptoms, it can be treated without surgery. An indeterminate one is studied further.
- Tessler FN et al. ACR Thyroid Imaging, Reporting and Data System (TI-RADS): White Paper of the ACR TI-RADS Committee. J Am Coll Radiol. 2017, 14(5): 587-595.
- Middleton WD et al. Multiinstitutional Analysis of Thyroid Nodule Risk Stratification Using the American College of Radiology Thyroid Imaging Reporting and Data System. AJR Am J Roentgenol. 2017, 208(6): 1331-1341.
- Cibas ES, Ali SZ. The 2017 Bethesda System for Reporting Thyroid Cytopathology. Thyroid. 2017, 27(11): 1341-1346.
