Kotaro Takahashi

Genomic profiling of meiotic errors and early malignant transformation events in ovarian mature teratoma

Abstract Ovarian mature teratoma (OMT) exhibits copy-neutral loss of heterozygosity (CN-LOH) derived from meiotic errors. Studies have classified OMT into five types using these CN-LOH patterns. However, tumor purity issues have hindered accurate classification and molecular characterization. Moreover, the relationship between OMT genomic abnormalities and malignant transformation remains unclear. Here, we used laser microdissection to selectively collect 29 epithelial regions from 22 OMT cases and 1 carcinoma in situ (CIS) region from a squamous cell carcinoma case arising from OMT. We then conducted whole-exome sequencing. Copy number analysis enabled classification according to the established system. In cases with multi-regional sampling, the CN-LOH patterns were identical within the same tumor, while bilateral tumors showed distinct patterns, indicating that each tumor originated independently. Among the type II OMTs, which are believed to result from meiosis II error, 2 cases exhibited a chromosomal gain. Assessment of heterozygosity suggested that these cases had meiosis I error before meiosis II error. Somatic mutation analysis revealed an extremely low mutation burden, with 1 case harboring a PIK3CA mutation. In the CIS region, additional copy number alterations were present alongside the underlying CN-LOH pattern. TP53 mutations and loss of the wild-type allele were detected. The tumor mutation burden of CIS was 6.2 mutations per megabase. Mutational signature analysis showed enrichment of apolipoprotein B mRNA editing enzyme catalytic subunit-associated signatures. This study suggests novel perspectives on the mechanisms of OMT tumor development and malignant transformation.

Clonal origin and genomic diversity in Lynch syndrome‐associated endometrial cancer with multiple synchronous tumors: Identification of the pathogenicity of MLH1 p.L582H

AbstractLynch syndrome‐associated endometrial cancer patients often present multiple synchronous tumors and this assessment can affect treatment strategies. We present a case of a 27‐year‐old woman with tumors in the uterine corpus, cervix, and ovaries who was diagnosed with endometrial cancer and exhibited cervical invasion and ovarian metastasis. Her family history suggested Lynch syndrome, and genetic testing identified a variant of uncertain significance, MLH1 p.L582H. We conducted immunohistochemical staining, microsatellite instability analysis, and Sanger sequencing for Lynch syndrome‐associated cancers in three generations of the family and identified consistent MLH1 loss. Whole‐exome sequencing for the corpus, cervical, and ovarian tumors of the proband identified a copy‐neutral loss of heterozygosity (LOH) occurring at the MLH1 position in all tumors. This indicated that the germline variant and the copy‐neutral LOH led to biallelic loss of MLH1 and was the cause of cancer initiation. All tumors shared a portion of somatic mutations with high mutant allele frequencies, suggesting a common clonal origin. There were no mutations shared only between the cervix and ovary samples. The profiles of mutant allele frequencies shared between the corpus and cervix or ovary indicated that two different subclones originating from the corpus independently metastasized to the cervix or ovary. Additionally, all tumors presented unique mutations in endometrial cancer‐associated genes such as ARID1A and PIK3CA. In conclusion, we demonstrated clonal origin and genomic diversity in a Lynch syndrome‐associated endometrial cancer, suggesting the importance of evaluating multiple sites in Lynch syndrome patients with synchronous tumors.

A retrospective study of Pipelle endometrial biopsy for ovarian, fallopian tube, and peritoneal cancers

Although the Pipelle endometrial biopsy is widely performed as a practical and minimally invasive test for endometrial disease(s), its effectiveness in ovarian cancer has not been explored. The aim of the present study was to evaluate the results of Pipelle endometrial biopsy for ovarian, fallopian tube, and peritoneal cancers. A pre-treatment Pipelle-endometrial biopsy was performed in 90 patients with ovarian, fallopian tube, or peritoneal cancers between January 2014 and November 2021. We retrospectively analysed the association between the results of Pipelle endometrial biopsy and clinicopathological data. Moreover, we evaluated their impact on the following treatment in advanced cases initially treated with chemotherapy. The sensitivity and false-negative rates for Pipelle endometrial biopsy were 25/90 (27.8%) and 65/90 (72.2%) in all patients, respectively, and 23/56 (41.0%) and 33/56 (58.9%) in cases with advanced disease (stages III and IV), respectively. Pipelle-positive endometrial biopsy-positive (Pipelle-positive) was not observed in 29 patients with clinical stage I disease, and Pipelle-positive patients exhibited significantly more high-grade serous carcinomas, and positive peritoneal, endometrial, and cervical cytologies than Pipelle-endometrial biopsy-negative cases. Surgical pathology was confirmed in 23 Pipelle-positive patients, and 17/23 (74.0%) had the same diagnosis as that for Pipelle endometrial biopsy. Conversely, 6/23 (26.0%) patients exhibited a minor diagnostic discrepancy between Pipelle endometrial biopsy and surgical pathology. Nineteen of the 38 (50.0%) patients initially treated with chemotherapy were identified as Pipelle-positive, contributing to a prompt histological diagnosis and pre-treatment tumour sampling. Companion diagnostic tests were performed using Pipelle endometrial biopsy samples from 4 inoperable patients. Although the positive rate of Pipelle endometrial biopsy in ovarian, fallopian tube, and peritoneal cancers is low, Pipelle endometrial biopsy may enable prompt histological diagnosis and initiation of chemotherapy while collecting tumour tissue for genetic testing in some cases with advanced disease.