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Specific mutations vary by race, age in pediatric thyroid cancer
More than half of children with well-differentiated thyroid carcinoma have mutations, with two types of mutations detected only in cases of papillary thyroid carcinoma and one mutation predominantly affecting adolescent Hispanic girls, according to study findings.
Ron S. Newfield, MD, associate clinical professor of pediatrics at University of California, San Diego, and colleagues analyzed thyroid tissue samples from 39 children with well-differentiated thyroid carcinoma — papillary thyroid carcinoma (PTC), follicular thyroid carcinoma (FTC) and follicular variant of PTC (FVPTC) — who underwent thyroidectomy at Rady Children’s Hospital–San Diego between 2001 and 2013 (29 girls; 22 Hispanic; mean age, 14.7 years; 28 cases of PTC; 89.7% of cases occurred after 2005). Patients with medullary carcinoma were excluded.
Researchers analyzed samples for BRAF V600E, NRAS, KRAS and HRAS point mutations and RET/PTC and PAX8/PPAR-gamma rearrangements using validated molecular methods.
Within the cohort, mutations were observed in 21 of 39 children; two of the mutations, BRAF V600E and RET/PTC, were detected only in cases of PTC (nine BRAF V600E cases and six RET/PTC cases).
Researchers observed two mutations out of five FTC cases (PAX8/PPAR-gamma and NRAS) and three mutations of six FVPTC cases (PAX8/PPAR-gamma).
Of 28 PTC patients, 57.1% had mutations: 32.1% with BRAF V600E; 21.4% with RET/PTC and 3.6% with NRAS.
Of patients with BRAF V600E, 77.8% were Hispanic and 88.9% were aged at least 15 years. All RET/PTC-positive patients were aged at least 15 years (P = .003).
Researchers found no significant mutation-based differences in tumor size, lymph node status or iodine-avid distant metastasis at diagnosis at the completion of initial treatment, according to researchers.
“This study demonstrates that in a pediatric population of [well-differentiated thyroid carcinoma] consisting mostly of Hispanic and Caucasian patients, the frequency of the BRAF V600E mutation is comparable to that found in the adult population, and it is mostly observed in those > 15 years old and of Hispanic descent,” the researchers wrote. “RET/PTC rearrangements were less prevalent in this cohort compared with prior pediatric studies. More advanced molecular analysis using next-generation sequencing will likely reveal other types of mutations, rearrangements and fusions that may affect the genotype–phenotype correlations.” – by Regina Schaffer
Disclosure: Some of researchers report employment with Quest Diagnostics.