Comparative analysis of EGFR gene mutations (exon 20) in sinonasal papillomas of inverted and oncocytic types

Sinonasal papillomas are a group of benign, relatively rare tumors of the sinonasal tract with varying clinical courses. In the modern WHO classification, it is customary to distinguish three subtypes of sinonasal papillomas: the most common inverted type (ISP), oncocytic type (OSP) and exophytic type (ESP). Recently, the concept has emerged that the different types of sinonasal papillomas may not be variants of a single tumor, but rather separate tumors. Thus, OSP demonstrates KRAS mutations, and the pathogenesis of ISP is associated with EGFR mutations. Objective. To provide a comparative description of the EGFR gene (exon 20) based on the results of Sanger sequencing in sinonasal papillomas of inverted and oncocytic types. Material and methods. Sanger sequencing of the EGFR gene (exon 20) was performed in 83 cases of sinonasal papillomas, of which 17 were of OSP and 66 were ISP cases. In 20 cases, an additional immunohistochemical study with an antibody to EGFR was also performed. Results. When sequencing by Sanger of exon 20 of the EGFR gene in the ISP group, missense mutations were identified in 16 out of 66 cases, leading to a change in the value of the coding sequence of the gene, ultimately determining the formation of a different amino acid; this type of mutation was not identified in the OSP group. The most common mutation was at position 2622 in the form of G to A transition: in 47 cases of ISP (70%) and in 12 cases of OSP (71%). This mutation was synonymous and did not lead to an amino acid replacement in the synthesized protein. Thus, we did not find any significant differences in exon 20 of the EGFR gene between the ISP and OSP groups. In the ISP group, in 48 of 66 cases, multiple and single point mutations were noted, which we characterize as genetic heterogeneity.