Mutational analysis of metastatic lymph nodes from papillary thyroid carcinoma in adult and pediatric patients.

Background: Limited data are available on the analysis of somatic mutations in metastatic lymph nodes in adult and pediatric patients with papillary thyroid carcinomas.

Methods: A total of 92, microdissected, formalin-fixed, paraffin-embedded tissue specimens from 39 patients were analyzed for the presence of somatic mutations utilizing the ThyGenX next-generation sequencing test.

Results: Somatic mutations were detected in 67% of papillary thyroid carcinoma specimens. The majority of patients with synchronous and all 6 patients with radioactive iodine-resistant (metachronous) metastatic lymph nodes contained BRAF mutations. Four patients had mutations detected in their metastatic lymph nodes that were not detected in their primary tumors. For the most part, BRAF mutations were seen in adults, and RAS mutations were seen in children.

Conclusion: Findings of different mutations in metastatic lymph nodes compared with the primary papillary thyroid carcinomas are probably the result of tumor heterogeneity. The presence of the BRAF mutation in metastatic lymph nodes might be responsible for the recurrence of papillary thyroid carcinomas and resistance to radioactive iodine therapy. The good prognosis observed in papillary thyroid carcinomas found in pediatric and young adult patients might be explained by the predominance of RAS rather than BRAF mutations.