New Protocol Helps Classify Thyroid Nodules in Children
Guidelines could help clinicians choose between invasive diagnostics and watchful waiting.
In the last several decades, the incidence of thyroid cancer has skyrocketed. But the death rate hasn’t changed. This suggests the spike is the result of increased medical imaging that incidentally detects thyroid nodules -- a general term for masses and irregularities in thyroid tissue that could be either benign or malignant -- while looking at something else, such as cervical vertebrae or the upper gastrointestinal tract.
When radiologists see evidence of nodules, they have to decide whether to pursue additional tests to determine if the nodules are malignant. The question is difficult in part because nodules are common but thyroid cancer is not, and most thyroid cancers are slow-growing and treatable. On the one hand, the clinician doesn’t want to put the patient through the risks associated with further testing, such as surgery to remove the nodule, or fine needle aspiration, which extracts a small amount of tissue and fluid from the gland for analysis. On the other hand, no one wants to miss treating a serious malignancy.
But the field is so imprecise at the moment, said Franklin Tessler, a diagnostic radiologist at the University of Alabama at Birmingham, that “a lot of people are flying by the seat of the pants.”
To clarify matters, in the last five years or so the thyroid and radiology societies have begun to publish best practice papers that stratify the risk based on the features of the nodules seen in the medical images, said Edward Grant, a professor of radiology at the Keck School of Medicine at the University of Southern California. Tessler and Grant helped develop one system for adults -- the American College of Radiology’s Thyroid Imaging, Reporting and Data System (ACR TI-RADS). This system has five descriptive categories: a nodule’s contrast with surrounding structures, the degree of margin smoothness, its texture, its shape, and the presence, number and shape of calcifications. The radiologist assigns each category a number from one to five, and the higher the total, the more suspicious the nodule is for cancer.
There is only one guideline system tailored to children -- the American Thyroid Association’s Management Guidelines for Children with Thyroid Nodules and Differentiated Thyroid Cancer. In 2016 radiologist Jennifer Lim-Dunham and colleagues at Loyola University Chicago Stritch School of Medicine and Medical Center in Maywood, Illinois, tested this system against a set of 39 thyroid nodules in 33 children who had undergone ultrasound-guided fine needle aspiration biopsy.
“We know that nodules in the thyroid that are blacker tend to be malignant,” said Lim-Dunham. “And [if] the edges of the nodule are more jagged, that’s a sign it’s more likely to be malignant.” Calcifications show up as white dots and can be associated with cancer.
Two radiologists viewed the ultrasound images and categorized them according to the ATA guidelines. The reviewers’ conclusions fitted perfectly with the actual tissue analyses, demonstrating the reliability of the criteria.
In 2017 the Lim-Dunham team did the same thing with the ACR TI-RADS system for a retrospective set of 74 thyroid nodule ultrasound scans from 62 children. This study confirmed the reliability of the ACR TI-RADS system.
Clearer diagnostic criteria could encourage physicians to recommend watchful waiting, in which a patient’s condition is monitored so that if something changes, it will be noticed, but the patient is spared invasive procedures.
Tessler, who chaired the ACR TI-RADS committee, said, “There is a reservoir of undiagnosed thyroid cancer, most of which would never cause harm to the patient. But the aim is to diagnose biologically significant cancers. Can we do that yet? I don’t think we’re quite there. If it turns out to show that ACR TI-RADS works well [in the pediatric population], that would be great.” Because the study has not yet been published in a peer-reviewed journal and he had not reviewed its methodology, Tessler cautioned that more evidence should accrue before the radiological community adopts the ACR TI-RADS wholesale for children, especially small children, whose risk of developing malignant nodules is higher.
Grant praised Lim-Dunham team’s work. “The TI-RADS scheme seems to work almost better in children than it does in adults,” he said.
Lim-Dunham presented the latest results at the May 2018 meeting of the Society for Pediatric Radiology and the study has been submitted to the American Journal of Roentgenology.