Conference Coverage

Bethesda system underpredicts malignancy in pediatric thyroid tumors


 

REPORTING FROM ATA 2019

In terms of the real-world outcomes in this cohort of pediatric patients with nodules, 14.8% of the 29 nodules with Bethesda category I – nondiagnostic – status were later found to be malignant, a higher rate than the 5%-10% expected in adults. Of 106 Bethesda category II – benign – nodules, 4% were malignant. In adults, 0%-3% of category II nodules turn out to be malignant.

Cytopathology from FNA of 22 nodules fell into the Bethesda category III, and 25% were malignant, which was within the expected range of 10%-30% for adults. “Bethesda class II accurately identified benign nodules with low risk of subsequent malignancy,” said Dr. Jiang.

Fourteen nodules were Bethesda category IV, and of those, 42.9% were malignant, again slightly higher than the 25%-40% expected in adults.

Just six nodules had FNA results falling into Bethesda category V, of which 83.3% were malignant, a higher rate than the 50%-75% expected for adult category V cytopathology results. All category V nodules were papillary thyroid carcinoma.

All 26 Bethesda category VI nodules were malignant; in adult category VI nodules, 97%-99% are expected to be malignant. All but four of the cases were found to be papillary thyroid carcinoma.

Dr. Jiang explained that at Rady Children’s Hospital, all FNA cytology slides received a second-opinion assessment by pathologists at the University of California San Diego. Of all the samples assessed in the study, there was disagreement about one slide, with a difference of one Bethesda category. “Malignant class cytology is quite reliable,” she said, adding the caveat that “second-opinion confirmation adds additional confidence to the cytologic diagnosis.”

She emphasized again that the initiation of on-site testing for sample adequacy significantly decreased the nondiagnostic rate seen over the course of the study.

Dr. Jiang reported no relevant conflicts of interest and no outside sources of funding.

SOURCE: Jiang W et al. ATA 2019, Oral Abstract 34.

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