Abstract
Cotyledonoid dissecting uterine leiomyoma (CDUL) is a rare subtype of uterine leiomyomata (UL) characterised by a large extrauterine component and disorganised, dissecting growth into the myometrium. Although UL are a common benign tumour of the uterine myometrium, there have only been 90 reported cases of CDUL, globally. Due to its rarity, CDUL has received limited scientific attention, with current published research consisting exclusively of clinical case reports and histology. To date, a genetic or epigenetic investigation has not been published.
We aimed to perform the first genetic and epigenetic profile of a CDUL case.
Tissue samples were obtained from the patient’s normal myometrium, a co-occurring typical UL, and the CDUL. Samples underwent histological analysis by a clinical pathologist, and DNA was isolated for both exome sequencing and reduced representation bisulphite sequencing. These two techniques provide genetic data for the coding regions and methylation states across the genome.
Parallel bioinformatic analyses were performed on the exomic and methylation data for each sample, with the goal of comparing significant features that may functionally contribute to CDUL development and progression. All data was quality controlled and aligned to the HG38 human reference genome. Differential methylation analysis and comparison of genomic variants between samples was performed using original code within R. The normal myometrium exome sample was used as the reference genome sequence to identify unique variants (SNPS and InDels) that occurred between the UL and CDUL samples. Variants were then annotated and assessed for biological significance using pathway analysis. In CDUL, 137 genes contained unique SNPs, and 837 genes contained unique InDels. In UL, 78 genes contained unique SNPs, and 626 genes contained unique InDels. Analysis of CDUL proved complicated due to extensive genomic re-arrangements, with no clear enrichment in biological pathways. However, mutated genes shared commonality with many malignant cancers. Aligned DNA methylation sequences were filtered for sequencing depth, and differentially methylated regions of DNA between the samples were annotated and compared. In the CDUL sample, widespread changes in DNA methylation were observed across the genome, with the most extensively affected genes associated with known cancer pathways, particularly PI3K/AKT. Further analysis is required to summarise genomic re-arrangements observed in the CDUL and to compare the UL sample to similar studies.
The genetic analysis of this CDUL sample provides a comparative basis for future studies. It does not appear we have detected candidate CDUL driver mutations; however, this first of its kind study will contribute towards further genetic and epigenetic research of CDUL tumourigenesis.