The clinical and molecular characterization of patients with dyshormonogenic congenital hypothyroidism reveals specific diagnostic clues for DUOX2 defects.

CONTEXT: Mutations in the DUOX2 gene have been associated with transient or permanent congenital hypothyroidism due to a dyshormonogenic defect. OBJECTIVE: This study aimed to verify the prevalence of DUOX2 mutations and the associated clinical features in children selected by criteria supporting a partial iodide organification defect (PIOD). PATIENTS AND METHODS: Thirty children with PIOD-like criteria were enrolled and genotyped. A detailed clinical characterization was undertaken together with the functional analysis of the DUOX2 variations and the revision of the clinical and molecular data of the literature. RESULTS: In this large selected series, the prevalence of the DUOX2 mutations was high (37%). We identified 12 missense variants, one splice site, and three frameshift DUOX2 mutations. Functional analyses showed significant impairment of H2O2 generation with five missense variants. Stop-codon mutants were shown to totally abolish DUOX2 activity by nonsense-mediated RNA decay, exon skipping, or protein truncation. DUOX2 mutations, either mono- or biallelic, were most frequently associated with permanent congenital hypothyroidism. Moreover, the present data suggested that, together with goiter and PIOD, the most significant features to select patients for the DUOX2 analysis are the low free T4 and the high TSH concentrations at the first postnatal serum sampling, despite borderline blood spot TSH. Interestingly, the analysis of previously described DUOX2 mutated cases confirmed the validity of these findings. CONCLUSIONS: The defects in the peroxide generation system are common among congenital hypothyroidism patients with PIOD. The most robust clinical parameters for selecting patients for DUOX2 analysis have been identified, and several DUOX2 variants have been functionally characterized.

Correlation between B-RAFV600E mutation and clinico-pathologic parameters in papillary thyroid carcinoma: data from a multicentric Italian study and review of the literature.

Recently, a somatic point mutation of the B-RAF gene (V600E) has been identified as the most common genetic event in papillary thyroid carcinoma (PTC), with a prevalence variable among different series. Since discordant data on the clinico-pathologic features of B-RAF mutated PTC are present in the literature, the aim of the present co-operative study was to establish the prevalence of this genetic alteration and to perform a genotype-phenotype correlation in a large cohort of patients with PTC. To this purpose, a series of 260 sporadic PTCs with different histological variants were included in the study. The mutational analysis of the B-RAF gene was performed either by RT-PCR followed by single-stranded conformational polymorphism or by PCR and direct sequencing. Statistical analyses were obtained by means of chi2/Fisher's exact test and t-test. Overall, a heterozygous T > A transversion at nucleotide 1799 (V600E) was found in 99 out of 260 PTCs (38%). According to the histological type of the tumor, the B-RAF (V600E) mutation was present in 48.3% of cases of classic PTCs (85 out of 176), in 17.6% (nine out of 51) of follicular variants of PTCs, in 21.7% (five out of 23) in other PTC variants and in none of the ten poorly differentiated tumors. B-RAF (V600E) was significantly associated with the classic variant of PTC (P = 0.0001) and with an older age at diagnosis (P = 0.01). No statistically significant correlation was found among the presence of B-RAF (V600E) and gender, tumor node metastasis (TNM), multicentricity of the tumor, stage at diagnosis and outcome. In conclusion, the present study reports the prevalence of B-RAF (V600E) (38%) in the largest series of sporadic PTCs, including 260 cases from three different Italian referring centers. This prevalence is similar to that calculated by pooling together all data previously reported, 39.6% (759 out of 1914 cases), thus indicating that the prevalence of this genetic event lies around 38-40%. Furthermore, B-RAF (V600E) was confirmed to be associated with the papillary growth pattern, but not with poorer differentiated PTC variants. A significant association of B-RAF mutation was also found with an older age at diagnosis, the mutation being very rare in childhood and adolescent PTCs. Finally, no correlation was found with a poorer prognosis and a worse outcome after a median follow-up of 72 months.

Medullary and papillary carcinoma of the thyroid gland occurring as a collision tumour: report of three cases with molecular analysis and review of the literature.

We report the simultaneous occurrence of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC), presenting as spatially distinct and well-defined tumour components, in three cases. In the first patient, histology, immunohistochemistry and electron microscopy demonstrated an MTC in the one nodule and PTC in two additional lesions. Non-neoplastic thyroid parenchyma separated the three nodules. Metastasis from PTC was diagnosed in a regional lymph node. Genetic analysis of both tumour components showed a distinctive mutational pattern: in the MTC a Cys634Arg substitution in exon 11 of the RET gene and in the two PTC foci a Val600Glu substitution in exon 15 of the BRAF gene. The other two patients are members of a large multigenerational family affected with familial MTC due to a germline mutation of the RET gene (Ala891Ser). Both patients harboured, besides medullary cancer and C-cell hyperplasia, distinct foci of papillary thyroid cancer, which was positive for Val600Glu BRAF mutation. Review of the literature disclosed 18 similar lesions reported and allowed the identification of different patterns of clinical presentation and biological behaviour. So far, the pathogenesis of these peculiar cases of thyroid malignancy has been completely unknown, but an underlying common genetic drive has been hypothesised. This is the first report in which two mutations, in the RET and BRAF genes, have been identified in three cases of MTC/PTC collision tumour, thus documenting the different genetic origin of these two coexisting carcinomas.