Ovarian clear cell carcinoma--bad endometriosis or bad endometrium?

New insights about endometriosis-associated ovarian cancer: pathogenesis, risk factors, prediction and diagnosis and treatment

Previous studies have shown that the risk of malignant transformation of endometriosis in premenopausal women is approximately 1%, significantly impacting the overall well-being and quality of life of affected women. Presently, the diagnostic gold standard for endometriosis-associated ovarian cancer (EAOC) continues to be invasive laparoscopy followed by histological examination. However, the application of this technique is limited due to its high cost, highlighting the importance of identifying a non-invasive diagnostic approach. Therefore, there is a critical need to explore non-invasive diagnostic methods to improve diagnostic precision and optimize clinical outcomes for patients. This review presents a comprehensive survey of the current progress in comprehending the pathogenesis of malignant transformation in endometriosis. Furthermore, it examines the most recent research discoveries concerning the diagnosis of EAOC and emphasizes potential targets for therapeutic intervention. The ultimate objective is to improve prevention, early detection, precise diagnosis, and treatment approaches, thereby optimizing the clinical outcomes for patients.

Review the progression of ovarian clear cell carcinoma from the perspective of genomics and epigenomics

Ovarian clear cell carcinoma (OCCC) is a rare subtype of epithelial ovarian cancer with unique molecular characteristics, specific biological and clinical behavior, poor prognosis and high resistance to chemotherapy. Pushed by the development of genome-wide technologies, our knowledge about the molecular features of OCCC has been considerably advanced. Numerous studies are emerging as groundbreaking, and many of them are promising treatment strategies. In this article, we reviewed studies about the genomics and epigenetics of OCCC, including gene mutation, copy number variations, DNA methylation and histone modifications.

Endometrial cancer with concomitant endometriosis is highly associated with ovarian endometrioid carcinoma: a retrospective cohort study

Background

Endometriosis is assumed to be involved in ovarian cancer development, which is called endometriosis-associated ovarian cancer (EAOC). Uterine endometrial cells may be the cell of origin of EAOC. Accumulated carcinogenic changes in the uterine endometrial cells may increase the risk of developing EAOC. To further understand the pathogenesis of EAOCs, we focused on the clinicopathological characteristics of EAOCs in endometrial cancer patients with concomitant endometriosis.

Methods

We retrospectively reviewed 376 patients who were surgically treated for stage I–III endometrial cancer. Clinicopathological characteristics were compared between patients with and without endometriosis. Furthermore, the incidence of simultaneous endometrial and ovarian cancer (SEOC) and the histological characteristics of SEOC were compared between the two groups.

Results

Among 376 patients with endometrial cancer, 51 had concomitant endometriosis. Patients with endometriosis were significantly younger and more frequently had endometrioid G1/G2 tumors than those without endometriosis. The incidence of SEOCs was significantly higher in endometrial cancer patients with endometriosis than those without it (p < 0.0001); notably, 12 of 51 endometrial cancer patients with endometriosis (24%) had SEOCs. All of the ovarian cancers in endometrial cancer patients with endometriosis were endometrioid carcinomas. Moreover, even in those without endometriosis, endometrioid carcinoma was the most common histological type of SEOC.

Conclusion

We revealed that endometrial cancer patients with endometriosis had a high probability of SEOC and that endometrioid carcinoma was the most common histological subtype of SEOC regardless of the presence of endometriosis. For patients with endometrial cancer and endometriosis, careful examination of ovarian endometriotic lesions may be important to detect EAOCs.

Adenomyosis as a Risk Factor for Myometrial or Endometrial Neoplasms-Review

Adenomyosis is a common benign gynecological condition, defined as an extension of endometrial tissue into the myometrium. Some studies suggest that adenomyosis could be a favorable prediction factor associated with survival outcomes in endometrial cancer. The aim of our systematic review was to investigate the current knowledge regarding adenomyosis and a possible molecular mechanism of carcinogenesis in adenomyotic lesions. In addition, the long-term prognosis for patients with endometrial cancer and coexisting adenomyosis (and endometriosis) was a key point of the research. The current literature was reviewed by searching PubMed, using the following phrases: "adenomyosis and endometrial cancer" and "malignant transformation of adenomyosis". According to the literature, genetic mutations, epigenetic changes, and inactivation of specific tumor suppressor genes in adenomyosis are still poorly understood. Data regarding the influence of adenomyosis on survival outcomes in endometrial cancer seem to be contradictory and require further clinical and molecular investigation.

Oestrogen up-regulates DNMT1 and leads to the hypermethylation of RUNX3 in the malignant transformation of ovarian endometriosis

RESEARCH QUESTION

What is the mechanism of hypermethylation of runt-related transcription factor 3 (RUNX3) in the eutopic endometrium of endometriosis as biomarker in the malignant transformation of endometriosis?

DESIGN

Methylation-specific polymerase chain reaction was used to analyse the methylation status of RUNX3 in endometriosis-associated ovarian cancer (EAOC). Primary eutopic endometrial stromal cells (ESC) were isolated from the uteri of patients with ovarian endometriosis. After RUNX3 knockdown by RNA interference technology or ESC treated with oestradiol, the proliferation and invasion ability were evaluated in ESC by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and transwell assays.

RESULTS

The frequency of methylation of RUNX3 in neoplastic tissue in the EAOC group was significantly higher than that in the ectopic endometrium of the endometriosis group (P < 0.001), and the frequency of methylation of RUNX3 in the eutopic endometrium of the EAOC group was significantly higher than that in the endometriosis group (P < 0.001). However, there was no significant difference in the eutopic endometrium when compared between the endometriosis group and the control endometrium group (P = 0.233). Silencing RUNX3 promoted the proliferation and invasion of ESC (P < 0.001 and P < 0.001). Following intervention with oestrogen, it was observed that the oestradiol group showed higher levels of RUNX3 methylation (P < 0.001) and DNA methyltransferase 1 (DNMT1) mRNA and protein expression (P < 0.001 and P < 0.001), and lower RUNX3 mRNA and protein expression when compared with the ESC group (P < 0.001 and P < 0.001).

CONCLUSION

This study demonstrated that hypermethylation of the RUNX3 was related to the malignant transformation of endometriosis and that this process was related to corresponding changes in the eutopic endometrium. Furthermore, the 'oestrogen-DNMT1' signalling pathway may induce the hypermethylation of RUNX3 to promote the malignant transformation of endometriosis.

Histopathology and ARID1A Expression in Endometriosis- Associated Ovarian Carcinoma (EAOC) Carcinogenesis Model with Endometrial Autoimplantation and DMBA Induction

BACKGROUND

Ovarian carcinoma is one of the most deadly malignancies in the gynecologic field. The cause is not yet known, and the clinical symptoms are not specific. Endometrioid carcinoma and ovarian clear cell carcinoma can originate from endometriosis and are known as endometriosis-related ovarian carcinoma (EAOC). Development of EAOC experimental animal models is needed for basic research and clinical preparation of human tissue tests. This study aimed to determine the role of the ARID1A gene mutation in the carcinogenetic process of EAOC in experimental animal models induced with DMBA.

METHODS

In this study, the EAOC experimental model was developed using the autoimplantation technique and DMBA induction. This study involved placebo surgery mice (sham), endometrial autoimplantation, and a combination of endometrial autoimplantation and DMBA induction, which were sacrificed at weeks 5, 10, and 20, respectively. Histopathological assessment and immunohistochemical ARID1A staining with an assessment of positive percentages were carried out on 200 cells.

RESULTS

This study produced 1 (20%) atypical endometriosis and 1 (20%) clear cell carcinoma at implantation and after 10 weeks of DMBA induction, and 100% endometrioid carcinoma in the DMBA-induced group. ARID1A staining did not show any significant difference (p = 0.313) in all groups.

CONCLUSION

The combination of endometrial autoimplantation techniques and DMBA induction in the ovary produced atypical endometriosis, clear cell carcinoma, and endometrioid carcinoma, where time is an important factor. There was no significant difference in ARID1A expression between the treatment and control groups.

Converging endometrial and ovarian tumorigenesis in Lynch syndrome: Shared origin of synchronous carcinomas

OBJECTIVE

The diagnosis of carcinoma in both the uterus and the ovary simultaneously is not uncommon and raises the question of synchronous primaries vs. metastatic disease. Targeted sequencing of sporadic synchronous endometrial and ovarian carcinomas has shown that such tumors are clonally related and thus represent metastatic disease from one site to the other. Our purpose was to investigate whether or not the same applies to Lynch syndrome (LS), in which synchronous cancers of the gynecological tract are twice as frequent as in sporadic cases, reflecting inherited defects in DNA mismatch repair (MMR).

METHODS

MMR gene mutation carriers with endometrial or ovarian carcinoma or endometrial hyperplasia were identified from a nationwide registry. Endometrial (n = 35) and ovarian carcinomas (n = 23), including 13 synchronous carcinoma pairs, were collected as well as endometrial hyperplasias (n = 56) and normal endometria (n = 99) from a surveillance program over two decades. All samples were studied for MMR status, ARID1A and L1CAM protein expression and tumor suppressor gene promoter methylation, and synchronous carcinomas additionally for somatic mutation profiles of 578 cancer-relevant genes.

RESULTS

Synchronous carcinomas were molecularly concordant in all cases. Prior or concurrent complex (but not simple) endometrial hyperplasias showed a high degree of concordance with endometrial or ovarian carcinoma as the endpoint lesion.

CONCLUSIONS

Our investigation suggests shared origins for synchronous endometrial and ovarian carcinomas in LS, in analogy to sporadic cases. The similar degrees of concordance between complex hyperplasias and endometrial vs. ovarian carcinoma highlight converging pathways for endometrial and ovarian tumorigenesis overall.

Predictive factors of ovarian carcinoma for women with ovarian endometrioma aged 45 years and older in China

BACKGROUND

To explore the risk factors of endometriosis-associated ovarian cancer (EAOC) in women with ovarian endometriosis (OEM) aged 45 years and above in China.

METHODS

This study reviewed the medical records of 1038 women in total who were aged 45 years and above, surgical-pathologically diagnosed with ovarian endometriosis, and were treated at Peking Union Medical College Hospital between December 1996 and December 2016. Histology evaluation was used to determine whether the ovarian endometriosis specimen was with (n = 30) or without (n = 1008) ovarian cancer.

RESULTS

2.9% (30/1038) of women with the surgical-pathological diagnosis of ovarian endometriosis were found to have EAOC. Those patients with EAOC were prone to be in the postmenopausal status at the time of the diagnosis (OR 5.50, 95%CI 2.54-11.90, P < .001) and larger size of tumor (≥8 cm, OR 7.19, 95% CI 3.34-15.50, P < .001), and higher prevalence of coexisting with endometrial disorders (OR 4.11, 95%CI 1.73-9.73, P = .003). This study showed that patients of an older age when diagnosed with OEM, were at a higher risk of developing EAOC, respectively measuring of 1.7% (13/751) at 45-49 years, 5.6% (12/215) at 50-54 years, and 10.0%(5/50) at 55-59 years (P < 0.001).

CONCLUSIONS

This study showed that for women aged 45 years and above who were diagnosed with OEM, the independent risk factors of EAOC were menopausal status, tumor size of 8 cm or greater in diameter, and coexisting endometrial disorders. Therefore, intensive follow-ups or active interventions should be considered for them.

Structural and calorimetric studies demonstrate that the hepatocyte nuclear factor 1β (HNF1β) transcription factor is imported into the nucleus via a monopartite NLS sequence

The transcription factor hepatocyte nuclear factor 1β (HNF1β) is ubiquitously overexpressed in ovarian clear cell carcinoma (CCC) and is a potential therapeutic target. To explore potential approaches that block HNF1β transcription we have identified and characterised extensively the nuclear localisation signal (NLS) for HNF1β and its interactions with the nuclear protein import receptor, Importin-α. Pull-down assays demonstrated that the DNA binding domain of HNF1β interacted with a spectrum of Importin-α isoforms and deletion constructs tagged with eGFP confirmed that the HNF1β (229)KKMRRNR(235) sequence was essential for nuclear localisation. We further characterised the interaction between the NLS and Importin-α using complementary biophysical techniques and have determined the 2.4Å resolution crystal structure of the HNF1β NLS peptide bound to Importin-α. The functional, biochemical, and structural characterisation of the nuclear localisation signal present on HNF1β and its interaction with the nuclear import protein Importin-α provide the basis for the development of compounds targeting transcription factor HNF1β via its nuclear import pathway.

Molecular pathogenesis of ovarian clear cell carcinoma

Ovarian clear cell carcinoma is a distinct subtype of epithelial ovarian cancer, characterized by an association with endometriosis, glycogen accumulation and resistance to chemotherapy. Key driver events, including ARID1A mutations and HNF1B overexpression, have been recently identified and their functional characterization is ongoing. Additionally, the role of glycogen in promoting the malignant phenotype is coming under scrutiny. Appreciation of the notion that ovarian clear cell carcinoma is essentially an ectopic uterine cancer will hopefully lead to improved animal models of the disease, in turn paving the way for effective treatments.

Tissue Factor-Factor VII Complex As a Key Regulator of Ovarian Cancer Phenotypes

Tissue factor (TF) is an integral membrane protein widely expressed in normal human cells. Blood coagulation factor VII (fVII) is a key enzyme in the extrinsic coagulation cascade that is predominantly secreted by hepatocytes and released into the bloodstream. The TF–fVII complex is aberrantly expressed on the surface of cancer cells, including ovarian cancer cells. This procoagulant complex can initiate intracellular signaling mechanisms, resulting in malignant phenotypes. Cancer tissues are chronically exposed to hypoxia. TF and fVII can be induced in response to hypoxia in ovarian cancer cells at the gene expression level, leading to the autonomous production of the TF–fVII complex. Here, we discuss the roles of the TF–fVII complex in the induction of malignant phenotypes in ovarian cancer cells. The hypoxic nature of ovarian cancer tissues and the roles of TF expression in endometriosis are discussed. Arguments will be extended to potential strategies to treat ovarian cancers based on our current knowledge of TF–fVII function.

The Association between Endometriomas and Ovarian Cancer: Preventive Effect of Inhibiting Ovulation and Menstruation during Reproductive Life

Although endometriosis frequently involves multiple sites in the pelvis, malignancies associated with this disease are mostly confined to the ovaries, evolving from an endometrioma. Endometriomas present a 2-3-fold increased risk of transformation in clear-cell, endometrioid, and possibly low-grade serous ovarian cancers, but not in mucinous ovarian cancers. These last cancers are, in some aspects, different from the other epithelial ovarian cancers, as they do not appear to be decreased by the inhibition of ovulation and menstruation. The step by step process of transformation from typical endometrioma, through atypical endometrioma, finally to ovarian cancer seems mainly related to oxidative stress, inflammation, hyperestrogenism, and specific molecular alterations. Particularly, activation of oncogenic KRAS and PI3K pathways and inactivation of tumor suppressor genes PTEN and ARID1A are suggested as major pathogenic mechanisms for endometriosis associated clear-cell and endometrioid ovarian cancer. Both the risk for endometriomas and their associated ovarian cancers seems to be highly and similarly decreased by the inhibition of ovulation and retrograde menstruation, suggesting a common pathogenetic mechanism and common possible preventive strategies during reproductive life.

ARID1A expression in ovarian clear cell carcinoma with an adenofibromatous component

AIMS

The carcinogenesis of ovarian clear cell carcinoma (CCC) has been hypothesized to comprise two different pathways: an adenofibroma-carcinoma sequence and an endometriosis-carcinoma sequence. However, the difference in the genetic basis of these two pathways remains unclear. Recent studies have suggested that an ARID1A mutation and the loss of the corresponding protein, BAF250a, are frequent events in CCC. Herein, we investigated the difference in the loss of BAF250a expression in adenofibroma-related CCC and endometriosis-related CCC.

METHODS AND RESULTS

In total, 93 cases of surgically treated CCC were evaluated. The presence of adenofibroma and endometriosis associated with carcinoma was determined by reviewing haematoxylin and eosin-stained slides for each case. BAF250a expression in carcinoma was examined immunohistochemically. The loss of BAF250a expression was detected in carcinomas in 50 of 93 (54%) cases, including five of 18 (28%) with adenofibroma alone, 30 of 45 (67%) with endometriosis alone, eight of 18 (44%) with both conditions and seven of 12 (58%) with neither condition. The loss of BAF250a expression was significantly less frequent in CCC cases with adenofibroma than in cases with endometriosis (P = 0.01, Fisher's exact test).

CONCLUSIONS

The action of ARID1A in carcinogenesis differs between adenofibroma-related CCC and endometriosis-related CCC.

The clinical characteristics and outcomes of cases with pure ovarian clear cell, mixed type and high-grade serous adenocarcinoma

PURPOSE

This study aimed to compare the clinical characteristics and outcomes of the cases with pure ovarian clear cell adenocarcinoma (OCCC), mixed type (clear plus serous or clear plus endometrioid or serous plus clear plus endometrioid) ovarian adenocarcinoma (MOC) and high-grade serous ovarian adenocarcinoma (HGSOC).

METHODS

A retrospective comparison was conducted in 32 cases with pure OCCC, 23 cases with MOC and 28 cases with HGSOC followed between January 1999 and October 2011. Clinico-pathologic characteristics including histopathologic subtypes, age, stage, presence of ascites and/or peritoneal carcinomatosis, endometriosis and optimal cytoreduction, and also survival rates were compared in these three groups.

RESULTS

The cases with pure OCCC were younger than the cases with MOC and HGSOC (p = 0.004). The median pre-operative CA-125 level was lower in the pure OCCC than in MOC and HGSOC (p = 0.006) (p = 0.001, p = <0.001, respectively). Bilaterality and peritoneal carcinomatosis were more frequently seen in the HGSOC group (p = 0.001, p < 0.001, respectively). The majority of the cases (65 %) had stage I or II disease in the pure OCCC group, but most of the cases in the HGSOC group had advanced stage disease (p < 0.001). Endometriosis was found in 16 cases (16/55, 29 %) in the OCCC group. No significant difference was detected with regard to the median survival rate among three groups (p = 0.517), while the stage of disease was found to be the only important factor for survival (p = 0.002).

CONCLUSION

Pure OCCC, MOC and HGSOC represent distinct clinical characteristics. Clinical characteristics of MOC are more similar to those of HGSOC.

Expression of LATS family proteins in ovarian tumors and its significance

Epithelial ovarian cancer is composed of a diverse group of tumors that can be derived from the fallopian tube, endometrium, or ovary. In this study, we explored the expression levels of LATS family members in ovarian tumors using normal ovaries, fallopian tubes, and endometrium as controls. Immunohistochemistry studies of LATS1, LATS2, Pax8, and calretinin were performed on normal ovary, fallopian tube, normal endometrium, and ovarian tumor sections. Statistical analyses were conducted using the χ(2) test, Fisher exact test, or Kruskal-Wallis H test. Patient survival was analyzed using the Kaplan-Meier method. LATS1 was expressed in normal ovarian epithelia, endometrium, and fallopian tubes, whereas LATS2 expression was observed in the normal fallopian tubes and endometrium. High expressions of LATS1 and LATS2 in serous cystadenomas gradually decreased in borderline cystadenomas and carcinomas, respectively. However, an opposite expression pattern was observed in mucinous tumors. Low expressions of LATS1 and LATS2 were also detected in clear cell carcinoma. Both LATS1 and LATS2 expression levels significantly correlated with recurrence and stage; LATS1 levels were also related with tumor grades in serous carcinoma. However, univariate and multivariate Cox regression analyses revealed that high expression of LATS1 was associated with better prognosis in patients with serous carcinoma. Both LATS1 and LATS2 were not related with the clinical variables in mucinous and clear cell carcinoma. LATS1 expression levels might be a valuable survival indicator in ovarian serous carcinoma.

Endometriosis, leiomyoma and adenomyosis: the risk of gynecologic malignancy

The aim of this review article was to evaluate the relationship and the possible etiological mechanisms between endometriosis, leiomyoma (LM) and adenomyosis and gynecological cancers, such as ovarian and endometrial cancer and leiomyosarcoma (LMS). MEDLINE was searched for all articles written in the English literature from July 1966 to May 2013. Reports were collected systematically and all the references were also reviewed. Malignant transformation of gynecologic benign diseases such as endometriosis, adenomyosis and LM to ovarian and endometrial cancer remains unclear. Hormonal factors, inflammation, familial predisposition, genetic alterations, growth factors, diet, altered immune system, environmental factors and oxidative stress may be causative factors in carcinogenesis. Early menarche, low parity, late menopause and infertility have also been implicated in the pathogenesis of these cancers. Ovarian cancers and endometriosis have been shown to have common genetic alterations such as loss of heterozygosity (LOH), PTEN, p53, ARID1A mutations. MicroRNAs have also been implicated in malignant transformation. Inflammation releases proinflammatory cytokines, and activates tumor associated macrophages (TAMS) and nuclear factor kappa b (NF-KB) signaling pathways that promote genetic mutations and carcinogenesis. MED12 mutations in LM and smooth muscle tumors of undetermined malignant potential (STUMP) may contribute to malignant transformation to LMS. A hyperestrogenic state may be shared in common with pathogenesis of adenomyosis, LM and endometrial cancer. However, the effect of these benign gynecologic diseases on endometrial cancer should be studied in detail. This review study indicates that endometriosis, LM, adenomyosis may be associated with increased risk of gynecological cancers such as endometrial and ovarian cancers. The patients who have these gynecological benign diseases should be counseled about the future risks of developing cancer. Further studies are needed to investigate the relationship between STUMPs, LMS and LM and characteristics and outcome endometrial carcinoma in adenomyotic patients.

Endometriosis and ovarian cancer

Endometriosis is the leading cause of morbidity among premenopausal women and the complex pathogenesis of this disease remains controversial despite extensive research. This disease represents one of the most common gynecological problems. It is generally believed that this disease is due primarily to retrograde menstruation or transplantation of shed endometrium. Based on overwhelming data, ovarian endometrioma is considered a neoplastic process, since most endometriosis-associated ovarian carcinoma occur in the presence of atypical ovarian endometriosis. A study comparing patients with typical epithelial ovarian cancer with endometriosis-associated ovarian cancer demonstrated that the patients with the latter disease strongly differ in both biological and histological characteristics. The prevelance of this disease is not completely established, but approximately 15 percent of women suffer from this disease. In addition, we know about the possible links between endometriosis and cancer for almost 100 years. Despite clear evidence revealing that endometriosis increases ovarian cancer risks, it is possible that it may not affect disease progression after the appearance of ovarian cancer. However, despite clear evidence revealing that endometriosis increases ovarian cancer risk, our knowledge of the risk factors is far from established. In our review, we focused on the most recent approaches including possible biomarkers and genetic approaches.

Prognostic analysis of endometrioid epithelial ovarian cancer with or without endometriosis: a 12-year cohort study of Chinese patients

OBJECTIVE

Clinicopathological characteristics and possible prognostic factors among women with endometrioid epithelial ovarian cancer (EEOC) with or without concurrent endometriosis were investigated.

STUDY DESIGN

A search of medical charts at Peking Union Medical College Hospital from 2000 through 2012 identified patients with EEOC with or without endometriosis.

RESULTS

Of 188 patients with EEOC, concurrent endometriosis was identified in 32 (17.0%). Patients with concurrent endometriosis were approximately 5 years younger, more likely to be premenopausal, more likely to have an early stage of EEOC, and less likely to have high-grade tumors compared to those without endometriosis. The univariate analysis showed that concurrent endometriosis was a significant prognostic factor for disease-free survival, but this association did not remain in the multivariate analysis.

CONCLUSION

Women with EEOC and concurrent endometriosis showed distinct characteristics and had longer disease-free survival when compared to those without endometriosis.

Cellular, histologic, and molecular changes associated with endometriosis and ovarian cancer

Our understanding of the pathogenesis of endometriosis is rapidly evolving as early molecular events are increasingly identified. Endometriosis is associated with increased risk of ovarian cancer and exhibits neoplastic phenotypes including invasion of stromal tissue and lymphatic spread to distant organs. This review of the literature establishes the clinical, epidemiologic, and pathologic correlation between endometriosis and low-grade ovarian cancer. Genetic studies have demonstrated that endometriotic lesions have mutations in genes directly related to neoplasms, in particular the p53, KRAS, PTEN, and ARID1A genes, which suggests a direct transition from a subset of endometriotic lesions to invasive carcinomas. The identification of both genetic and epigenetic biomarkers including microRNAs are essential for identifying patients at risk for the transition to neoplasia.

The occurrence of endometriosis with ovarian carcinomas is not purely coincidental

OBJECTIVE

To explore the association between epithelial ovarian cancer (EOC) and common benign gynecological disorders.

STUDY DESIGN

The medical records of 226 patients with EOC treated at Peking Union Medical College Hospital between March 2011 and March 2012 were reviewed. Histological evaluations had been performed to determine the presence of coexisting pelvic endometriosis (n=17), uterine leiomyoma (n=66), adenomyosis (n=22), or endometrial polyps (n=17).

RESULTS

Coexistence of endometriosis occurred in 35.3% and 36.4% of cases of the clear cell and endometrioid subtypes of EOC histology, respectively. Endometriosis was more likely associated with clear cell or endometrioid ovarian carcinoma, but less likely with high grade serous cancer. No differences were observed in the concurrence of uterine myoma, adenomyosis or endometrial polyps among the different subtypes of EOC.

CONCLUSIONS

In contrast to other common benign gynecological disorders, endometriosis showed close relationships with the clear cell and endometrioid subtypes of EOC specifically.

Epigenetic analysis leads to identification of HNF1B as a subtype-specific susceptibility gene for ovarian cancer

HNF1B is overexpressed in clear cell epithelial ovarian cancer, and we observed epigenetic silencing in serous epithelial ovarian cancer, leading us to hypothesize that variation in this gene differentially associates with epithelial ovarian cancer risk according to histological subtype. Here we comprehensively map variation in HNF1B with respect to epithelial ovarian cancer risk and analyse DNA methylation and expression profiles across histological subtypes. Different single-nucleotide polymorphisms associate with invasive serous (rs7405776 odds ratio (OR)=1.13, P=3.1 × 10(-10)) and clear cell (rs11651755 OR=0.77, P=1.6 × 10(-8)) epithelial ovarian cancer. Risk alleles for the serous subtype associate with higher HNF1B-promoter methylation in these tumours. Unmethylated, expressed HNF1B, primarily present in clear cell tumours, coincides with a CpG island methylator phenotype affecting numerous other promoters throughout the genome. Different variants in HNF1B associate with risk of serous and clear cell epithelial ovarian cancer; DNA methylation and expression patterns are also notably distinct between these subtypes. These findings underscore distinct mechanisms driving different epithelial ovarian cancer histological subtypes.