TR4 on a thyroid ultrasound means a nodule scored 4 to 6 points on the ACR TI-RADS system and is classified as “moderately suspicious.” It sits in the middle of a five-level scale that radiologists use to estimate how likely a thyroid nodule is to be cancerous, with TR1 (benign) at the bottom and TR5 (highly suspicious) at the top. A TR4 result does not mean you have cancer. The estimated cancer risk for TR4 nodules is roughly 5 to 9%, depending on the population studied.
How the Scoring System Works
ACR TI-RADS (Thyroid Imaging Reporting and Data System) was developed by the American College of Radiology to standardize how radiologists evaluate thyroid nodules. Instead of relying on subjective impressions, the system assigns points based on five specific features visible on ultrasound: composition, echogenicity, shape, margins, and echogenic foci. The radiologist picks one finding from each category, adds up the points, and the total determines the TR level.
The five levels are:
- TR1 (0 points): Benign
- TR2 (2 points): Not suspicious
- TR3 (3 points): Mildly suspicious
- TR4 (4–6 points): Moderately suspicious
- TR5 (7+ points): Highly suspicious
A TR4 nodule lands in that 4-to-6 range, which means it has a combination of features that raise some concern but doesn’t stack up enough worrisome characteristics to reach the highest category.
What Features Push a Nodule Into TR4
Each ultrasound feature carries a different point value. Knowing how the points add up can help you understand why your nodule was scored the way it was.
Composition looks at whether the nodule is solid, partially fluid-filled, or completely cystic. A solid nodule scores 2 points, while a purely cystic one scores 0. Echogenicity describes how bright or dark the nodule appears compared to surrounding thyroid tissue. A nodule that appears darker than normal tissue (hypoechoic) scores 2 points; one that’s much darker (very hypoechoic) scores 3.
Shape matters too. A nodule that is taller than it is wide, measured on a cross-sectional view, scores 3 points because this orientation is more commonly seen in cancerous nodules. A wider-than-tall shape scores 0. Margins are scored based on whether the edges look smooth (0 points), lobulated or irregular (2 points), or extend beyond the thyroid gland (3 points).
The final category, echogenic foci, covers calcifications and other bright spots within the nodule. Tiny punctate bright spots (often representing microcalcifications) add 3 points and are the most concerning finding in this category. Larger calcifications add 1 point, and rim calcifications add 2. Unlike the other categories where you pick one, multiple findings here can be counted together.
A common TR4 scenario: a solid, hypoechoic nodule with smooth margins, wider-than-tall shape, and no calcifications would score exactly 4 points (2 for solid + 2 for hypoechoic). Add a single macrocalcification and it becomes 5 points, still TR4.
Cancer Risk for TR4 Nodules
In the dataset used to develop TI-RADS, about 9.1% of TR4 nodules turned out to be cancerous. That dataset had a higher-than-typical overall cancer rate of 10.3%, though, because it included a large proportion of nodules that were already biopsied. When researchers adjusted for a more realistic real-world cancer rate of 5%, the estimated risk for a TR4 nodule dropped to about 4.6%.
Put another way, roughly 90 to 95 out of every 100 TR4 nodules are benign. TR4 is the single largest category, making up about 37% of all scored nodules in that development dataset. Most people who receive a TR4 result will not have thyroid cancer, but the score is high enough that further evaluation is typically recommended depending on the nodule’s size.
When Biopsy Is Recommended
A TR4 classification alone doesn’t automatically trigger a biopsy. The ACR guidelines pair the suspicion level with the nodule’s size to decide next steps. For TR4, the standard recommendation is fine needle aspiration (FNA) biopsy for nodules 1.5 centimeters or larger. For nodules between 1.0 and 1.5 cm, follow-up ultrasound is the usual approach rather than immediate biopsy.
FNA is a quick outpatient procedure where a thin needle is inserted into the nodule, often guided by ultrasound, to collect a small sample of cells. It’s the most reliable way to determine whether a nodule is benign or malignant without surgery.
Some institutions have adopted slightly more aggressive thresholds, recommending biopsy for TR4 nodules at 1.0 cm or larger and follow-up imaging for those as small as 0.5 cm. These modified strategies aim to catch smaller cancers, particularly in younger patients, though they also lead to more biopsies of nodules that turn out to be benign.
Follow-Up for Smaller TR4 Nodules
If your TR4 nodule doesn’t meet the size threshold for biopsy, your doctor will likely recommend a repeat ultrasound to monitor it over time. The goal is to watch for growth or changes in appearance that might push the nodule into biopsy territory. Stable nodules that don’t change over several imaging cycles are reassuring.
Certain factors can influence whether your doctor recommends biopsy even for a smaller nodule. A history of radiation exposure to the head or neck, a strong family history of thyroid cancer, or signs of suspicious lymph nodes nearby may lower the size threshold for biopsy. Nodule location also plays a role: nodules in the isthmus (the thin bridge connecting the two thyroid lobes) carry a higher cancer risk than those in the lower part of the lobe. Symptoms like persistent cough or voice changes, which can suggest the nodule is pressing on or invading nearby structures, also factor into the decision.
What TR4 Does Not Tell You
TI-RADS is a screening tool, not a diagnosis. It estimates probability based on how a nodule looks, but ultrasound alone cannot confirm or rule out cancer. Many features that earn points, like a solid composition or slightly darker appearance, are extremely common in benign nodules. The scoring system is deliberately designed to cast a wide net so that potentially dangerous nodules aren’t missed, which means it also flags many harmless ones.
If your nodule is biopsied, the pathology results (reported using the Bethesda system) will give a much clearer picture of whether the cells are benign, indeterminate, or malignant. Most TR4 nodules that go to biopsy come back benign.