About one-third of endometrial carcinomas (ECs), mainly of endometrioid histology, harbor the mismatch repair (MMR) defects and microsatellite instability (MSI). Among these, ECs arising in women with Lynch syndrome (LS) account for a large proportion. To date, no somatic genetic analyses have been published comparing LS-ECs with sporadic ECs. In this work, we examined the mutational profiles of a well-characterized series of sporadic and LS-related ECs, performing exonic targeted sequencing of 16 genes mainly involved in MSI ECs. Next-generation sequencing analysis was performed in 35 ECs on the MiSeq platform (Illumina, San Diego, CA), and the mutational profile was analyzed integrating molecular and immunohistochemical data. PTEN, ARID1A, and ARID2 were the most frequently mutated genes regardless of MSI status or family history. MSI ECs showed a higher mutational load than MMR-proficient cases, exhibiting an MMR-deficient mutational signature. Among MSI tumors, LS-related and sporadic ECs exhibited similar mutational profiles, with MSH2 as the most commonly mutated gene. KRAS mutations seemed to be more common in sporadic MSI ECs than in LS-related ECs even if further studies are needed to confirm this finding. MMR-deficient ECs carried a higher mutational load and an excess of C>T transitions compared with MMR-proficient ECs, suggesting that the use of a small gene panel may be adequate to highlight significant differences between these 2 groups. An integrated analysis of genetic and epigenetic features of LS-related and sporadic ECs provides useful insights into disease biology and diagnostic classification of these tumors.
Keywords: ARID1A; Endometrial cancer; Lynch syndrome; MLH1 silencing; MMR defect; Targeted sequencing.
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