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.
Reference List:
Soelberg KK, Bonnema SJ, Brix TH, Hegedüs L. Risk of malignancy in thyroid incidentalomas detected by 18F-fluorodeoxyglucose positron emission tomography: a systematic review. Thyroid. 2012 Sep;22(9):918-25. doi: 10.1089/thy.2012.0005.Epub 2012 Jul 24. Review. PubMed PMID: 22827552.
Pattison DA, Bozin M, Gorelik A, Hofman MS, Hicks RJ, Skandarajah A. (18)F-FDG-Avid Thyroid Incidentalomas: The Importance of Contextual Interpretation. J Nucl Med. 2018 May;59(5):749-755. doi: 10.2967/jnumed.117.198085. Epub 2017 Oct 12. PubMed PMID: 29025986.
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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.
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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).
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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.
Reference List:
Tessler FN, Middleton WD, Grant EG. Thyroid Imaging Reporting and Data System (TI-RADS): A User's Guide. Radiology. 2018 Jun;287(3):1082. doi:10.1148/radiol.2018184008. PubMed PMID: 29782241.
Middleton WD, Teefey SA, Reading CC, Langer JE, Beland MD, Szabunio MM, Desser TS. Multiinstitutional Analysis of Thyroid Nodule Risk Stratification Using the American College of Radiology Thyroid Imaging Reporting and Data System. AJR Am J Roentgenol. 2017 Jun;208(6):1331-1341. doi:10.2214/AJR.16.17613. Epub 2017 Apr 12. PubMed PMID: 28402167.
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FAQ-115: If a nodule has been previously biopsied, do you continue to apply TI-RADS to it or just report size?
We give an ACR TI-RADS classification for previously-biopsied nodules, but say that management should be at least partially guided by the biopsy results, and don’t give a specific recommendation. For the ACR TI-RADS registry study, these nodules do not need to be described using the full study template. If necessary, you may use free text to describe the nodules.
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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?
As stated in the white paper, ACR TI-RADS does not address previously-biopsied nodules. We follow the ATA’s recommendations, which appear under Recommendation 23 in their 2015 guidelines. Essentially, they say that high suspicion nodules require a follow-up US and FNA, with lesser follow-up for less suspicious nodules. We encourage referring to the ATA guidelines document for details.
Haugen BR, Alexander EK, Bible KC, Doherty GM, Mandel SJ, Nikiforov YE, Pacini F, Randolph GW, Sawka AM, Schlumberger M, Schuff KG, Sherman SI, Sosa JA, Steward DL, Tuttle RM, Wartofsky L. 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid. 2016 Jan;26(1):1-133. doi: 10.1089/thy.2015.0020. Review. PubMed PMID: 26462967; PubMed Central PMCID: PMC4739132.