FAQ-111: How do you handle PET positive thyroid nodules?
PET-positive thyroid nodules have a relatively high malignancy rate of 35%. In a patient with normal life expectancy, a biopsy should be performed for nodules >1cm regardless of the ACR TI-RADS risk category.
However, many patients undergoing a PET scan will have another malignancy. Pattison et al. performed a retrospective study that showed the median overall survival of patients with incidental FDG18 avid thyroid nodules was 20 months due to death from the primary malignancy. Since these patients often have serial imaging, it is reasonable to observe the incidental nodules in many of them.
FAQ-112: Do you have specific recommendations for nodules that have demonstrated a “significant” increase in size?
In general, if a nodule grows significantly (as defined in the white paper), its new size determines management for its TR level. For example, a nodule that formerly was below the threshold for FNA may warrant biopsy because of interval enlargement.
FAQ-113: If you don’t use the terms “moderately or highly suspicious” in your report for nodules whose sizes do not meet the criteria for FNA, how do you report the findings in the impression?
2.0 cm right TR3 nodule for which follow-up ultrasound in 1 year is recommended. We usually do not report nodules that require neither FNA nor follow-up in the impression unless attention was called to them for some reason (e.g., MRI, prior sonogram).
FAQ-114: I am still quite uncomfortable making a dramatic shift from reporting nodules based on size to the recommendation of completely ignoring ones that need no follow-up or FNA. Even more so, I feel insecure making no follow-up recommendation for a solid TIRADS 4 nodule that happens to be less than 1 cm. Especially when the TIRADS 4 category states these are “Moderately Suspicious”. I feel a bit exposed.
The ACR TI-RADS recommendations for FNA and follow-up were in part informed by the growing recognition that many thyroid cancers are indolent and unlikely to cause harm to patients during their lifetime. The prevalence of malignancy in all T4 nodules is 9%, with a range of 6%, 10%, and 13 % for nodules with 4, 5, and 6 points respectively (Middleton AJR 2017), and if it is malignant, it is likely to be indolent when it is small.
Nevertheless, we recognize that patients are increasingly able to view imaging reports though portals and other means and that they may be concerned that an 8 mm TR4 nodule described as “moderately suspicious” will not be biopsied or even followed-up. For this reason, radiologists may elect not to mention the risk descriptors in reports.
By no means are we advocating withholding information; rather, we wish to avoid misinterpretation by patients who may not fully understand the difference in clinical importance between a moderately suspicious thyroid nodule and a similarly suspicious pulmonary lesion.
FAQ-115: If a nodule has been previously biopsied, do you continue to apply TI-RADS to it or just report size?
Yes. In patients undergoing systemic therapy, radiologists at their discretion may apply the treatment response algorithm to assess lesions after locoregional therapy. Radiologists may not apply this algorithm to assess the treatment response of other lesions in such patients, however.
FAQ-116: What do you do with nodules that are already biopsy-proven to be benign but somehow come back for follow-up? If a nodule increases in size but is still TR4, do you still recommend follow-up or re-biopsy because of the size increase?
A category of LR-TR Nonevaluable should be assigned if treatment response cannot be meaningfully evaluated due to inappropriate imaging technique or inadequate imaging quality. Do not assign a response category of nonevaluable if image quality is adequate, even if imaging features are difficult to characterize or interpret.