The simultaneous occurrence of endometrial and ovarian cancer, known as synchronous cancer (SEOC), occurs in approximately 5% of cases of endometrial cancer and 10% of cases of ovarian carcinoma [1], and it is estimated that up to 14% are caused by Lynch syndrome [2, 3].

Lynch syndrome (LS) is an autosomal dominant cancer syndrome characterized by a high risk of predominantly colorectal and endometrial cancer (lifetime risk of up to 60%), but also ovarian, pancreatobiliary, urinary tract, brain, and sebaceous gland cancers [4, 5]. It is caused by germline mutation in one of the DNA mismatch repair (MMR) genes - MLH1 (3p22), MSH2 (2p21), MSH6 (2p16), PMS2 (7p22), MLH3 (14q24), MLH2 (2q32) [6]. According to Knudson’s hypothesis, the pathogenesis of hereditary cancers, particularly LS, starts with a first hit - an inherited germline mutation in tumor suppressor genes (MMR genes). The second hit is somatic mutation, leads to inactivation of the MMR mechanism, resulting in accumulation of numerous mutations, most evident in repetitive DNA during replication [7]. This tumorigenesis in LS causes the following characteristics of tumors - microsatellite instability (MSI), loss of MMR proteins, and a high number of somatic mutations, all of listed above together are referred to as MMR deficiency [8, 9]. MMR deficiency can also occur in some sporadic cases of colorectal (CRC) and endometrial cancer (EC), and the most common cause is hypermethylation of the MLH1 promoter, leading to loss of expression of the MLH1 and PMS2 proteins [10].

The differentiation of tumors into LS and sporadic cases is very important for the follow-up of patients with LS and for their relatives [11]. More recently, the widespread introduction of “universal screening” for LS (all cases with CRC and all EC cases diagnosed before age 60 should be tested for MMR deficiency) [12, 13] has led to an increasing number of suspected LS cases- MMR-deficient tumors without germline mutation in the MMR genes. These cases are attributed to the so-called Lynch-like syndrome (LLS) [14]. LLS tumors have been shown to account for up to 70% of patients with MSI and MMR suspected for LS [15, 16]. The prevalence of LLS is 56–71% in CRC and between 30 and 64% in EC [17]. Thus, the prevalence of cases with LLS is approximately twice as high in both CRC and EC as in LS.

The aetiology of LLS is not yet clear, but three possible mechanisms are suspected: (a) germline mutation in other genes involved in MMR that could also cause MMR deficiency in tumor tissue, (b) germline mutation in MMR genes that cannot be identified due to the insufficiency of the performed DNA test, (c) somatic mutations within tumor cells causing the same MMR deficiency. Therefore, LLS patients are a heterogeneous group that includes sporadic cases with biallelic MMR deficiency and inherited cases related to pathogenic germline variants in other DNA repair genes [18, 19]. LLS cases cannot be easily attributed to inherited or sporadic MMR deficiency, which complicates the management of patients. Carriers of hereditary MMR deficiency and their carrier relatives are at high risk for a second primary carcinoma or for developing cancer and they should be referred for prevention. In contrast, individuals with somatic inactivation of MMR and their relatives are not at such increased risk. While the risk of cancer in cases with LS is generally higher than in general population (particularly for CRC and EC) and there are guidelines for the treatment and surveillance for these patients and their relatives [20, 21], the risk of cancer associated with LLS is unclear. Different studies show conflicting results regarding age of diagnosis, risk of CRC and EC [19].

The genetic basis of hereditary LLS is not yet fully understood. With the advent of next generation sequencing (NGS) and the ability to test many cancer-predisposing genes simultaneously, many have been shown to cause inherited cases of LLS - MUTYH [22], genes involved in cell activity regulation (EXO1, POLD1, RCF1, and RPA1) [23], BUB1 and BUB3 [24], SETD2 [24], WRN [25], BARD1 [25], and other genes that promote genomic integrity [25].

We present a case of LLS with synchronous endometrial and ovarian cancer and detected germline pathogenic variant in the WRN gene.

The index patient (proband) was referred to the Center of Medical genetics in University Hospital “Dr. Georgi Stranski” – Pleven for germline genetic testing. Blood sample was obtained (in EDTA tube) from the patient after informed consents.

Tumor sample used in the present study was collected after obtaining informed consent for participation in the study. Endometrial tumor specimens from the proband was fixed in 10% buffered formalin for 24–36 h at room temperature, dissected and paraffin embedded. A pathologist selected 5 μm thick parallel sections of representative invasive tumor material and normal mucosa, and the tissue sample was confirmed to contain cancerous tissue using hemoxylin and eosin staining, which was performed as routine. Epitope retrieval time for all tumor sections was 20 min at 97˚C in DAKO PT Link (cat. no. PT100/PT101). Tumor sections were stained with the following antibodies (all from Dako, Agilent Technologies, Inc., and all came ready to use): ES05Monoclonal mouse AntiHuman MutL Protein Homolog 1, (cat. no. IR079), FE11Monoclonal mouse AntiHuman MutS Protein Homolog 2 (cat. no. IR085), EP49Monoclonal rabbit AntiHuman MutS Protein Homolog 6 (cat. no. IR086), and EP51Monoclonal rabbit AntiHuman Postmeiotic Segregation Increased 2 (cat. no. IR087) for MLH1, MSH2, MSH6 and PMS2 respectively. Incubation time for all antibodies was 20 min at room temperature. Staining was done with Autostainer Link 48 (Dako Agilent) slide stainer was used according to the manufacturer’s protocol. The external negative controls were the negative reagent controls included in the kit.For internal positive controls were used normal endometrial mucosa, stromal cells and stromal lymphocytes from the same patients. Results were analyzed manually by a pathologist. Expression was reported as: Normal, (retained expression) nuclear expression in > 10% tumor cells and retained expression in the internal control or Negative, (loss of expression) 0% expression in tumor cells and retained expression in the internal control.

Genomic DNA was isolated from blood sample using MagCore Genomic DNA Whole blood Kit according to the manifacturer’s protocol.

The genetic testing of the proband was performed by next generation sequencing (NGS). Trusight Cancer Sequencing Panel (Illumina©) was used for library preparation. The pan-hereditary cancer panel contained oligo probes targeting 94 genes and 284 SNPs associated with increased cancer predisposition. The procedures following the manufacturer’s instructions. Qualified libraries were sequenced on the Illumiina NextSeq 550 platform with 2 × 150 bp configuration. Reads were aligned to the reference human genome hg19. Data output files (gVCF) were imported into BaseSpace Variant Interpreter (Illumina©). Custom filters (included a minimum read depth of 20x per variant and excluded silent variants) were created to improve variant annotation and interpretation. The five-tier terminology system of the American College of Medical Genetics and Genomics (ACMG) was used for variant classification [26], including: Pathogenic (P), Likely Pathogenic (LP), Variant of Unknown clinical significance (VUS), Likely Benign (LB), and Benign (B). The variants automatically annotated by the software were manually checked in the main human genome databases: ClinVar (www.ncbi.nlm.noh.gov/clinvar), dbSNP (www.ncbi.nlm.noh.gov/projrct/SNP), and Ensembl (http://www.ensembl.org).