Analysis by Next-Generation Sequencing Panel Covered 60 Genes and 17 Microsatellite Foci in Endometrial Screening Liquid-Based Cytology Specimens A Comparative Study to Tissue Specimens

Abstract

BackgroundLiquid-based cytology (LBC) is now a widely used method for cytologic screening and diagnosis of cancers. Since the cells are fixed with alcohol-based fixatives and the specimens are stored in a liquid condition, LBC specimens are also conducive for genetic analysis. MethodsHere, we established a small cancer gene panel including 60 genes and 17 microsatellite markers for next-generation sequencing and applied to residual LBC specimens obtained by endometrial cancer screening to compare with corresponding formalin-fixed paraffin-embedded (FFPE) tissues. ResultsA total of 53 FFPE and LBC specimens (n=24) were analyzed, revealing characteristic mutations for endometrial cancer including those of PTEN, CTNNB1, PIK3CA, and PIK3R1 . Eight cases had higher scores for both tumor mutation burden (TMB) and microsatellite instability (MSI), which agree with defective mismatch repair (MMR) protein expression. Paired endometrial LBC, and biopsied and/or resected FFPE tissues from 7 cases, demonstrated almost the same mutations, TMB, and MSI profiles in all cases. ConclusionThese findings demonstrate that the small cancer gene panel proved to be able to detect therapeutically actionable gene mutations in endometrial LBC and FFPE specimens and that LBC specimens obtained by endometrial cancer screening is an alternative and useful source of molecular testing. BackgroundEndometrial cancer is the most common gynecologic cancer worldwide, affecting over 500,000women every year [1]. Since lifestyle changes can affect the risk of developing endometrial cancer, an epidemiological approach is essential to manage the disease [2]. Moreover, genome-wide association studies have identified new susceptibility loci for endometrial cancer in the human genome, providing candidate genes for further studies that aim to unravel the mechanisms driving 4 carcinogenesis, which could offer new opportunities for early screening and detection or identification of therapeutic targets [3]. Unlike squamous cell carcinoma of the uterine cervix with pathogenesis closely related to that of human papilloma virus infection [4], endometrial carcinogenesis is linked to common cancer gene mutations and genome instability [5,6].Cytology specimens including conventional smear, cytospin, liquid-based cytology (LBC), and cell block are valuable sources of routine molecular diagnostics [7]. In fact, extensive studies have been reported that variety of cytology materials, containing LBC specimens, are available for molecular testing by next-generation sequencing (NSG), especially in non-small cell lung cancer [7][8][9][10][11][12].Meanwhile, the endometrial cytology is not only safe and easy clinical procedure but also comparable to suction endometrial biopsy for detecting atypical endometrial hyperplasia and cancers [13][14][15][16].Since 1987 in Japan, a cytologic examination for endometrial cancer screening is established by a national health insurance low. Thereafter, endometrial cytology using a specific device is introduced as a less invasive and less...