Dados do Resumo

Título

Beta-catenin differential expression in salivary gland tumors: an immunohistochemical and molecular study

Introdução

Salivary gland tumors present a wide morphologic variation, especially among neoplasms with prominent or partial involvement of myoepithelial component. Currently, there are few studies correlating histologic subtypes with genetic alterations in benign and malignant salivary gland tumors. Understanding the molecular basis of these lesions would be useful for differential diagnosis and classification by evaluating their mutational profiles. Therefore, beta-catenin expression and mutational status may help to understand some of the pathways involved in tumorigenesis.

Objetivo

The aim of this study is beta-catenin analysis in benign and malignant samples of salivary gland tumors, by comparing immunohistochemistry (IHC) expression and molecular changes using Next Generation Sequencing (NGS) to verify the differences between tumor subtypes.

Métodos

We selected 28 cases pleomorphic adenoma, 03 myoepithelioma, 07 basal cell adenoma, 08 carcinoma ex-pleomorphic adenoma, 04 myoepithelial carcinoma and 03 basal cell adenocarcinoma cases in which paraffin material was available. Given the rarity and genetic preservation protocol, DNA extraction was performed, and 15 samples were qualified for quantity and integrity. For NGS of the DNA samples, the Ion AmpliSeq Comprehensive Cancer Panel (Thermo Fisher Scientific, USA) was used, which contains 409 genes frequently mutated in cancer. Sequencing was performed on the Ion GeneStudio S5 Plus platform according to the manufacturer's instructions. The analysis was performed using Torrent Suite 5.12.3 and Varseq 2.2.5 software, following the quality requirements. Variants affecting the coding region of the protein were selected. In this step, we observed 81 alterations, but after critical filtering such as an allelic frequency, pathway and databases, we selected 5 genes to follow for validation in 31 DNA samples available. The CTNNB1 was completed, with a focus on hotspots sites and the changes observed in IHC and NGS was compared (CEP protocol 2706/19).

Resultados

Of the 31 samples sequenced in the specific exon, 27 samples also had immunohistochemical analysis that can be compared. The analyses were carried out manually using the BAM files in the IGV program and their classification reviewed in the Franklin database. Among these comparisons we can highlight: the identification of nuclear staining in basal cell adenoma cases and a VUS alteration in codon 35. One case of basal cell adenocarcinoma showed nuclear staining with an alteration in codon 26 and another case of basal cell adenocarcinoma showed discontinuous membrane labeling and two pathogenic alterations in codons 40 and 45. Finally, four cases of carcinoma ex-pleomorphic adenoma showed membrane staining but with different pathogenic alterations. And the cases of myoepithelial carcinoma also showed membrane staining and the same alteration in codon 34, also considered pathogenic.

Conclusões

Few alterations were observed in the tumors, and we can observe differences especially when comparing basal cell adenoma and adenocarcinoma. Further studies are necessary to investigate the influence and the role of beta-catenin in these tumors.

Financiador do resumo

CAPES

Palavras Chave

salivary gland tumors; Next Generation Sequence; beta-catenin