Mutational Analysis in Pediatric Thyroid Cancer and Correlations with Age, Ethnicity, and Clinical Presentation.

BACKGROUND: Well-differentiated thyroid cancer (WDTC) incidence in pediatrics is rising, most being papillary thyroid carcinoma (PTC). The objective of the study was to assess the prevalence of different mutations in pediatric WDTC and correlate the genotype with the clinical phenotype. METHODS: This is a single-center retrospective study. Thyroid tissue blocks from 42 consecutive pediatric WDTC patients who underwent thyroidectomy between 2001 and 2013 were analyzed at Quest Diagnostics for BRAF(V600E), RAS mutations (N,K,H), and RET/PTC and PAX8/PPARγ rearrangements, using validated molecular methods. Thyroid carcinomas included PTC, follicular thyroid carcinoma (FTC), and follicular variant of PTC (FVPTC). RESULTS: Thirty-nine samples (29 females) were genotyped. The mean age at diagnosis was 14.7 years (range 7.9-18.4 years), and most were Hispanic (56.4%) or Caucasian (35.9%). The mean follow-up period was 2.9 years. Mutations were noted in 21/39 (53.8%), with both BRAF(V600E) (n = 9), and RET/PTC (n = 6) detected only in PTC. Mutations were detected in 2/5 FTC (PAX8/PPARγ and NRAS) and 3/6 FVPTC cases (PAX8/PPARγ). 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 >15 years, while all RET/PTC-positive patients were ≤15 years (p = 0.003). Tumor size, lymph node involvement, and distant metastasis at diagnosis (or soon after (131)I ablation) did not vary significantly based on the mutation. CONCLUSIONS: BRAF(V600E) was the most common mutation, especially in older and Hispanic adolescents. A larger, ethnically diverse pediatric cohort followed long term will enable the genotypic variability, clinical presentation, and response to therapy to be better assessed.

Detection of BRAF V600 mutations in metastatic melanoma: comparison of the Cobas 4800 and Sanger sequencing assays.

Detection of the BRAF V600E mutation is required for use of the BRAF inhibitor, vemurafenib, in patients with metastatic melanoma. Although the Roche Cobas 4800 BRAF V600 Mutation Test is approved, it detects primarily the single-nucleotide V600E mutation and could miss other potentially relevant V600 mutations. To assess the detection rate of the cobas assay for V600 mutations in clinical specimens, we compared the results of this assay with Sanger sequencing in 295 melanoma FFPE samples. Twenty samples were excluded because of invalid results on the cobas (n = 3), sequencing (n = 15), or both (n = 2). V600 mutations were detected by the cobas test in 96 (34.9%) of 275 samples and by Sanger sequencing in 118 (42.9%) of 275 samples. Thus, relative to Sanger sequencing, the cobas test exhibited 80.5% sensitivity (95% CI, 72.4% to 86.6%) and 99.4% specificity (95% CI, 96.5% to 99.9%). Of 23 samples with positive sequencing results but negative cobas results, 21 harbored dinucleotide mutations (V600E in 6, V600K in 10, and V600R in 5); the other two involved single-nucleotide mutations (V600E and V600G). These findings indicate that the cobas assay may miss many V600 mutations in clinical specimens. In our study, the addition of Sanger sequencing for samples with negative cobas results increased the detection rate to 42.9%. This approach could help maximize the number of patients who benefit from BRAF inhibitor treatment.

Functional delay of myelination of auditory delay lines in the nucleus laminaris of the barn owl.

In the barn owl, maps of interaural time difference (ITD) are created in the nucleus laminaris (NL) by interdigitating axons that act as delay lines. Adult delay line axons are myelinated, and this myelination is timely, coinciding with the attainment of adult head size, and stable ITD cues. The proximal portions of the axons become myelinated in late embryonic life, but the delay line portions of the axon in NL remain unmyelinated until the first postnatal week. Myelination of the delay lines peaks at the third week posthatch, and myelinating oligodendrocyte density approaches adult levels by one month, when the head reaches its adult width. Migration of oligodendrocyte progenitors into NL and the subsequent onset of myelination may be restricted by a glial barrier in late embryonic stages and the first posthatch week, since the loss of tenascin-C immunoreactivity in NL is correlated with oligodendrocyte progenitor migration into NL.