Tubal and ovarian pathways to pelvic epithelial cancer: a pathological perspective

Ovarian Cancer Is an Imported Disease: Fact or Fiction?

The cell of origin of ovarian cancer has been long debated. The current paradigm is that epithelial ovarian cancer (EOC) arises from the ovarian surface epithelium (OSE). OSE is composed of flat, nondescript cells more closely resembling the mesothelium lining the peritoneal cavity, with which it is continuous, rather than the various histologic types of ovarian carcinoma (serous, endometrioid, and clear cell carcinoma), which have a Müllerian phenotype. Accordingly, it has been argued that the OSE undergoes a process termed "metaplasia" to account for this profound morphologic transformation. Recent molecular and clinicopathologic studies not only have failed to support this hypothesis but also have provided evidence that EOC stems from Müllerian-derived extraovarian cells that involve the ovary secondarily, thereby calling into question the very existence of primary EOC. This new model of ovarian carcinogenesis proposes that fallopian tube epithelium (benign or malignant) implants on the ovary to give rise to both high-grade and low-grade serous carcinomas, and that endometrial tissue implants on the ovary and produces endometriosis, which can undergo malignant transformation into endometrioid and clear cell carcinoma. Thus, ultimately EOC is not ovarian in origin but rather is secondary, and it is logical to conclude that the only true primary ovarian neoplasms are germ cell and gonadal stromal tumors analogous to tumors in the testis. If this new model is confirmed, it has profound implications for the early detection and treatment of "ovarian cancer."

Gene expression profiling reveals differentially expressed genes in ovarian cancer of the hen: support for oviductal origin?

Ovarian cancer has a high mortality rate due, in part, to the lack of early detection and incomplete understanding of the origin of the disease. The hen is the only spontaneous model of ovarian cancer and can therefore aid in the identification and testing of early detection strategies and therapeutics. Our aim was to combine the use of the hen animal model and microarray technology to identify differentially expressed genes in ovarian tissue from normal hens compared with hens with ovarian cancer. We found that the transcripts up-regulated in chicken ovarian tumors were enriched for oviduct-related genes. Quantitative real-time PCR and immunohistochemistry confirmed expression of oviduct-related genes in normal oviduct and in ovaries from hens with early- and late-stage ovarian tumors, but not in normal ovarian surface epithelium. In addition, one of the oviduct-related genes identified in our analysis, paired box 2 has been implicated in human ovarian cancer and may serve as a marker of the disease. Furthermore, estrogen receptor 1 mRNA is over-expressed in early-stage tumors, suggesting that expression of the oviduct-related genes may be regulated by estrogen. We have also identified oviduct-related genes that encode secreted proteins that could represent putative serum biomarkers. The expression of oviduct-related genes in early-stage tumors is similar to what is seen in human ovarian cancer, with tumors resembling normal Müllerian epithelium. These data suggest that chicken ovarian tumors may arise from alternative sites, including the oviduct.

Oral contraceptives decrease the prevalence of ovarian cancer in the hen

Ovarian cancer is the leading cause of reproductive cancer death in U.S. women. This high mortality rate is due to the lack of early detection methods and ineffectiveness of therapy for advanced disease. Until more effective screening methods and therapies are developed, chemoprevention strategies are warranted. The hen has a high spontaneous prevalence of ovarian cancer and has been used as a model for studying ovarian cancer chemoprevention. In this study, we used the hen to determine the effect of progestin alone, estrogen alone, or progestin and estrogen in combination (as found in oral contraceptives) on ovarian cancer prevalence. We found that treatment with progestin alone and in combination with estrogen decreased the prevalence of ovarian cancer. A significant risk reduction of 91% was observed in the group treated with progestin alone (risk ratio = 0.0909; 95% CI: 0.0117-0.704) and an 81% reduction was observed in the group treated with progestin plus estrogen (risk ratio = 0.1916; 95% CI = 0.043-0.864). Egg production was also significantly reduced in these treatment groups compared with control. We found no effect of progestin, either alone or in combination with estrogen, on apoptosis or proliferation in the ovary, indicating that this is not the likely mechanism responsible for the protective effect of progestin in the hen. Our results support the use of oral contraceptives to prevent ovarian cancer and suggest that ovulation is related to the risk of ovarian cancer in hens and that other factors, such as hormones, more than likely modify this risk.

Prognostic and diagnostic significance of DNA methylation patterns in high grade serous ovarian cancer

OBJECTIVE

Altered DNA methylation patterns hold promise as cancer biomarkers. In this study we selected a panel of genes which are commonly methylated in a variety of cancers to evaluate their potential application as biomarkers for prognosis and diagnosis in high grade serous ovarian carcinoma (HGSOC); the most common and lethal subtype of ovarian cancer.

METHODS

The methylation patterns of 10 genes (BRCA1, EN1, DLEC1, HOXA9, RASSF1A, GATA4, GATA5, HSULF1, CDH1, SFN) were examined and compared in a cohort of 80 primary HGSOC and 12 benign ovarian surface epithelium (OSE) samples using methylation-specific headloop suppression PCR.

RESULTS

The genes were variably methylated in primary HGSOC, with HOXA9 methylation observed in 95% of cases. Most genes were rarely methylated in benign OSE, with the exception of SFN which was methylated in all HGSOC and benign OSE samples examined. Methylation of DLEC1 was associated with disease recurrence, independent of tumor stage and suboptimal surgical debulking (HR 3.5 (95% CI:1.10-11.07), p=0.033). A combination of the methylation status of HOXA9 and EN1 could discriminate HGSOC from benign OSE with a sensitivity of 98.8% and a specificity of 91.7%, which increased to 100% sensitivity with no loss of specificity when pre-operative CA125 levels were also incorporated.

CONCLUSIONS

This study provides further evidence to support the feasibility of detecting altered DNA methylation patterns as a potential diagnostic and prognostic approach for HGSOC.

Tubal origin of 'ovarian' low-grade serous carcinoma

Ovarian low-grade serous carcinomas are thought to evolve in a stepwise fashion from ovarian epithelial inclusions, cystadenomas, and borderline tumors. The current study was designed to gain insight into the origins of low-grade serous carcinomas (tubal versus ovarian) by comparatively evaluating the morphologic (secretory and ciliated cell distribution) and immunophenotypic (using antibodies to PAX8, tubulin, calretinin, and Ki67) attributes of its putative precursor lesions, the normal tubal epithelium, and the overt malignancy. A total of 226 adnexal tissues from 178 patients were studied, including 98 adnexae removed for non-neoplastic indications, 48 serous cystadenomas, 42 serous borderline tumors, and 38 low-grade serous carcinomas. Normal distal tubal epithelium comprised an admixture of PAX8+/tubulin- secretory cells and PAX8-/tubulin+ ciliated cells with a proliferative index of ∼3%. The vast majority of ovarian surface epithelia displayed a mesothelial phenotype (calretinin+/PAX8-/tubulin-) and low proliferative index (0% (12 per 1000)), although 4% of cases also displayed foci with tubal phenotype (calretinin-/PAX8+/tubulin+). In contrast, most (78%) of the ovarian epithelial inclusions displayed a tubal phenotype and had a significantly higher proliferative index (1%) than ovarian surface epithelium, indicating that in most cases, the ovarian surface epithelium and ovarian epithelial inclusions are of different lineages. There was a progressive decrease in the population of ciliated cells, as evidenced by increasing secretory/ciliated cell ratio, from ovarian epithelial inclusions/cystadenomas to borderline tumors to low-grade serous carcinoma, indicating that the latter is a clonal expansion of secretory cells. Overall, the findings make a strong argument that the ovarian epithelial inclusions with a tubal phenotype is likely derived from fallopian tube through an intraovarian endosalpingiosis rather than through Mullerian metaplasia from ovarian surface epithelium. Genetic and molecular studies are needed to further confirm this finding as tubal origination of ovarian serous cancers will have a significant impact on ovarian cancer prevention and management.

The impact of ovulation on fallopian tube epithelial cells: evaluating three hypotheses connecting ovulation and serous ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy affecting American women. Current hypotheses concerning the etiology of ovarian cancer propose that a reduction in the lifetime number of ovulations decreases ovarian cancer risk. Advanced serous carcinoma shares several biomarkers with fallopian tube epithelial cells, suggesting that some forms of ovarian carcinoma may originate in the fallopian tube. Currently, the impact of ovulation on the tubal epithelium is unknown. In CD1 mice, ovulation did not increase tubal epithelial cell (TEC) proliferation as measured by bromodeoxyuridine incorporation and proliferating cell nuclear antigen staining as compared to unstimulated animals. In superovulated mice, an increase in the number of pro-inflammatory macrophages was detected in the oviduct. Ovulation also increased levels of phospho-γH2A.X in TEC, indicating that these cells were susceptible to double-strand DNA breakage following ovulation. To determine which components of ovulation contributed to DNA damage in the fallopian tube, an immortalized baboon TEC cell line and a three-dimensional organ culture system for mouse oviduct and baboon fallopian tubes were developed. TEC did not proliferate or display increased DNA damage in response to the gonadotropins or estradiol alone in vitro. Oxidative stress generated by treatment with hydrogen peroxide or macrophage-conditioned medium increased DNA damage in TEC in culture. Ovulation may impact the fallopian tube epithelium by generating DNA damage and stimulating macrophage infiltration but does not increase proliferation through gonadotropin signaling.

Prevalence of epithelial ovarian cancer stem cells correlates with recurrence in early-stage ovarian cancer

Epithelial ovarian cancer stem cells (EOC stem cells) have been associated with recurrence and chemoresistance. CD44 and CK18 are highly expressed in cancer stem cells and function as tools for their identification and characterization. We investigated the association between the number of CD44+ EOC stem cells in ovarian cancer tumors and progression-free survival. EOC stem cells exist as clusters located close to the stroma forming the cancer stem cell “niche”. 17.1% of the samples reveled high number of CD44+ EOC stem cells (>20% positive cells). In addition, the number of CD44+ EOC stem cells was significantly higher in patients with early-stage ovarian cancer (FIGO I/II), and it was associated with shorter progression-free survival (P = 0.026). This study suggests that quantification of the number of EOC stem cells in the tumor can be used as a predictor of disease and could be applied for treatment selection in early-stage ovarian cancer.

Early stage (IA-IB) primary carcinoma of the fallopian tube: case-control comparison to adenocarcinoma of the ovary

OBJECTIVE

Early stage primary carcinoma of the fallopian tube (PCFT) is an uncommon condition when strict criteria are applied. The aim of this study was to compare the outcome stage IA-IB PCFT to a matched group of ovarian cancer (OC).

METHODS

Between 1990 and 2008, 32 patients with stage IA-IB of PCFT were recorded in the database of three French Institutions. A control group of patients with OC was constituted.

RESULTS

Eleven eligible PCFT cases and 29 OC controls fulfilled the stringent inclusion criteria. Median follow-up was 70.2 months. Five-year overall survival was 83.3% (95% confidence interval [CI], 27.3 to 97.5) for PCFT and 88.0% (95% CI, 66.9 to 96.0) for OC (p=0.93). In the subgroup of patients with grade 2-3, the outcome was similar in PCFT compared to OC patients (p=0.75). Five-year relapse-free survival was respectively 62.5% (95% CI, 22.9 to 86.1) and 85.0% (95% CI, 64.6 to 94.2) in the PCFT and OC groups (p=0.07). In the subgroup of patients (grade 2-3), there was no difference between PCFT and OC (p=0.65).

CONCLUSION

The findings did not reveal any difference in prognosis between early stage of PCFT and OC when grade is taken into account. Management of PCFT should mirror that of ovarian carcinoma.

Identification of abrogated pathways in fallopian tube epithelium from BRCA1 mutation carriers

The discovery of occult invasive and intra-epithelial tubal carcinomas in BRCA1 mutation carriers undergoing prophylactic surgery has implicated the fallopian tube epithelium as the source of serous cancer. However, little is known of the early molecular events of serous oncogenesis, or why cancers in BRCA1 mutation carriers are found preferentially in tissues which are responsive to reproductive hormones. We hypothesize that molecular alterations present in morphologically normal tubal epithelium from BRCA1 heterozygotes reflect the earliest events in serous carcinogenesis and may be markers of increased cancer risk as well as targets for risk reduction. Genetic profiling of microdissected tubal epithelium from histologically normal BRCA1 mutation carriers and controls was performed. We sought to define a signature which differentiated BRCA1 mutant tubal epithelium from women with low risk of developing ovarian cancer. Molecular differences between the follicular and luteal phases were prominent and, by using filtering techniques and a two-way ANOVA without a False Discovery Rate correction, we identified 440 probe sets with a more than two-fold change in gene expression related to BRCA1 mutation status. Using gene ontology and known associations to cancer pathways, we selected five genes for further analysis by qPCR and immunohistochemistry, and were able to demonstrate statistically significant differentiation of BRCA1 and control cases in an independent set of cases. The altered expression profiles in histologically normal tubal epithelium from BRCA1 heterozygotes suggest that these cells may respond differently to microenvironmental stresses.

Increased incidence of endometrioid tumors caused by aberrations in E-cadherin promoter of mismatch repair-deficient mice

Loss of E-cadherin expression is a critical step in the development and progression of gynecological tumors. Study of the precise role of E-cadherin has been hampered by the lack of satisfactory mouse model for E-cadherin deficiency. Likewise, DNA mismatch repair (MMR) is implicated in gynecological tumorigenesis, but knockout of MMR in mice predominantly causes hematologic neoplasms. Here, we show that combined disruption of E-cadherin and DNA MMR pathways increases incidence of endometrioid tumors in mice. Twenty percent of mice knockout for Msh2 enzyme and hemizygous for E-cadherin [Msh2(-/-)/Cdh1(+/-)] developed endometrioid-like tumors in the ovary, uterus and genital area. Characteristic of these tumors was a complete loss of E-cadherin expression. Sequence analysis of E-cadherin promoter region demonstrated that the loss of E-cadherin expression is caused by inactivating mutations, implying that E-cadherin is a mutational target in Msh2-deficient mice. In addition, Msh2(-/-)/Cdh1(+/-) mice showed a reduction in overall survival as compared with their Msh2(-/-) counterparts due to the development of more aggressive lymphomas, suggesting a specific role of E-cadherin in lymphomagenesis. In conclusion, Msh2(-/-)/Cdh1(+/-) mice provide a good model of gynecological tumorigenesis and may be useful for testing molecular target-specific therapies.

Ovarian epithelial-stromal interactions: role of interleukins 1 and 6

Ovarian epithelial cancer is the most lethal gynecologic malignancy. The high mortality is attributed to the fact that most cases typically present in late stage when ovarian cancer (OC) has already spread beyond the ovary. Ovarian epithelial cancer cells are shed into intraperitoneal ascites and easily disseminate throughout the peritoneal cavity with preferential metastasis to the omentum, peritoneum, and local organs. Understanding how ovarian epithelial cells interact with and modulate their microenvironment can provide insight into the molecular mechanism(s) involved with malignant transformation and progression which may eventually identify novel diagnostic, prognostic, and therapeutic targets. The objective of this paper is to provide a brief consideration of ovarian surface epithelial-stromal interactions in regard to normal physiological function and tumor progression as influenced by two potentially key interleukins, interleukins-1 (IL-1) and -6 (IL-6), present in the microenvironment. Lastly, we will consider the clinical implications of IL-1 and IL-6 for OC patients.

Anti-proliferative and pro-apoptotic actions of a novel human and mouse ovarian tumor-associated gene OTAG-12: downregulation, alternative splicing and drug sensitization

In studying the age dependence and chronology of ovarian tumors in follicle stimulating hormone receptor knockout mice, we identified a novel ovarian tumor associated gene-12 (OTAG-12), which is progressively downregulated and maps to Chr. 8B3.3. OTAG-12 protein overexpression in mouse ovarian and mammary tumor cells suggested powerful anti-proliferative effects. In human epithelial ovarian cancers (OCs) and OC cell lines, OTAG-12 mRNA expression is downregulated in comparison with normal ovaries. Cloning and identification revealed that human OTAG-12 mapping to gene-rich Chr. 19p13.12 is expressed in three spliced forms: hOTAG-12a, hOTAG-12b and hOTAG-12c, of which b is predominant in the normal ovary. Functionally active hOTAG-12b is a simple protein with no disulfide bonds and a nuclear localization signal is present in all variants. Transfection of OTAG-12 variants in OC and tumorigenic HEK293 cells confirmed nuclear localization. hOTAG-12b overexpression in OC and HEK293 cells effectively suppressed cell growth, anchorage-dependent and independent colony formation followed by apoptosis, whereas hOTAG-12a and hOTAG-12c had no such effects. Deletion mutants identified the critical importance of carboxyl terminus for hOTAG-12b function. Doxycycline-inducible growth inhibition of HEK293 cells by hOTAG-12a was associated with effects on G2 cell cycle arrest and apoptosis induction. hOTAG-12b expression rendered tumorigenic cells more sensitive to four apoptotic stimuli including etoposide-a topoisomerase-II inhibitor. Doxycycline-induced hOTAG-12b expression blocked xenograft tumor growth in nude mice, whereas hOTAG-12a was ineffective. Although p53-pathway-dependent apoptotic agents could upregulate endogenous hOTAG-12b and p53 in UCI-101/107 OC cells, hOTAG-12b could also induce apoptosis in p53-null and platinum-resistant SKOV3 OC cells and Doxycycline-induced hOTAG-12b did not alter p53. Further study showed that hOTAG-12b increases mRNAs of pro-apoptotic genes such as BAD, GADD45α and CIEDB, while inhibiting anti-apoptotic NAIP and Akt1 expression, suggesting that hOTAG-12b-induced apoptosis might be p53-independent. These results indicate that hOTAG-12b is a putative ovarian tumor suppressor gene warranting further studies.

Risk factors for carcinoma of the fallopian tube in women with and without a germline BRCA mutation

OBJECTIVE

The purpose of this study was to identify risk factors for fallopian tube cancer in women with and without a BRCA mutation.

METHODS

Subjects with fallopian tube cancer were identified from two sources: 1) a large international registry of women who carry a BRCA1 or BRCA2 mutation (n=56), and; 2) a population-based study of ovarian and fallopian tube cancer conducted in Ontario, Canada (n=66). BRCA mutation status was established for all subjects. Each subject was matched to one or more unaffected controls, for date of birth (within four years), for BRCA mutation status (negative, BRCA1, and BRCA2), for country of residence and for past history of breast cancer (yes/no). All subjects completed a questionnaire about medical history and lifestyle factors. Odds ratios and 95% confidence intervals were calculated for parity, oral contraceptive use, tubal ligation, hormone replacement therapy and body mass index, using conditional logistic regression.

RESULTS

We studied 103 women with fallopian tube cancer (48 with a BRCA1 mutation, 12 with a BRCA2 mutation and 43 with no identified BRCA mutation) and 980 matched controls. Increasing parity was associated with a decreased risk of fallopian tube cancer in non-carriers (trend per birth odds ratio 0.71 (95% CI 0.52-0.97), p=0.03), in BRCA1 carriers (OR=0.79 (0.62-1.02) p=0.07) and in BRCA2 carriers (OR=0.62 (0.34-1.15), p=0.13), but was statistically significant only for non-carriers. Oral contraceptive use was associated with a reduced risk in BRCA1 carriers (trend per year of use odds ratio=0.91 (0.83-0.99), p=0.03) but not for non-carriers (OR=0.97 (0.87-1.09), p=0.64) or for BRCA2 carriers (OR=0.94 (0.80-1.11), p=0.47). Hormone replacement therapy was associated with an increased risk for fallopian tube cancer in all subjects (OR=1.07 (1.01-1.13), p=0.03), and in the subgroups stratified by mutation, however the association was not significant in the subgroups. Tubal ligation was associated with a decreased risk of fallopian tube cancer for all subjects (OR=0.64 (0.31-1.28), p=0.21), however the reduction was not significant.

CONCLUSIONS

Parity and oral contraceptive use are associated with reduced risks of fallopian tube cancer. In contrast, hormone replacement therapy may be associated with an increase in the risk of fallopian tube cancer.

The emerging role of the distal Fallopian tube and p53 in pelvic serous carcinogenesis

In their paper in this issue of the Journal, Xian et al have analysed in detail the Fallopian tubes from two patients with Li-Fraumeni syndrome (germline TP53 mutation) in order to investigate further the possible role of p53 signatures in the development of high-grade pelvic serous carcinoma. They find an increased frequency of p53 signatures, with associated evidence of DNA damage and loss of heterozygosity at the wild-type TP53 allele, but postulate, as Li-Fraumeni syndrome is not associated with an increased risk of pelvic serous carcinoma, that these events are not sufficient for the development of carcinoma. Rather, they put forward a model postulating that further events, particularly loss of BRCA1/2 function, are required for lesion progression. This paper exemplifies how the hypothesis-driven study of a rare syndrome can be highly effective at answering specific questions about disease processes. It is of note that recent evidence from the same group provides convincing evidence that the distal Fallopian tube may, in fact, be the commonest site of origin for high-grade pelvic serous carcinomas, most of which may originate at this site rather than from the ovary. In addition to its biological significance, this, if proven, has clear clinical implications.

Molecular pathogenesis of endometrial and ovarian cancer

Pregnancy, breastfeeding, and oral contraceptive pill use interrupt menstrual cycles and reduce endometrial and ovarian cancer risk. This suggests the importance of turnover within Mullerian tissues, where the accumulation of mutations in p53 and PTEN has been correlated with number of cycles. The most common type of endometrial cancer (Type I) is endometrioid and molecular abnormalities include mutations in PTEN, KRAS and β-catenin. The Type I precursor is Endometrial Intraepithelial Neoplasia which displays PTEN defects. Type II endometrial cancer (whose precursors are less clear) includes serous and clear cell tumors and the most common alteration is p53 mutation. For ovarian cancer, histopathologic types parallel endometrial cancer and include serous, mucinous, endometrioid, and clear cell; some molecular features are also shared. The most frequent type of ovarian cancer is high grade serous that often displays p53 mutation and its precursor lesions may originate from normal-appearing fallopian tube epithelium that contains a p53 "signature". Mutations in KRAS, BRAF and PTEN are described in mucinous, endometrioid and low grade serous cancers and these may originate from ovarian cortical inclusion cysts. A consideration of molecular and other pathogenetic features, like epidemiology and histopathology, may provide a better understanding of endometrial and ovarian cancer.

Proteogenomic studies in epithelial ovarian cancer: established knowledge and future needs

There has been a concerted effort over the last decade to improve our understanding of the complex biology of ovarian cancer. A linear growth in published proteogenomic studies has addressed a variety of questions regarding its molecular pathogenesis. A number of genes have been identified by transcriptomic approaches, some of which are being investigated as putative tumor markers (HE4, OPN, Ep-CAM and Mesothelin), whilst others are potential targets for molecular therapeutic approaches (VEGF, IO4, EGFR, MUC1, CLDN4 and SLPI). Proteogenomics has the potential to further change our current characterization and treatment of ovarian cancer. Additional advances will depend on integrated study designs, interdisciplinary collaborations, use of robust high-throughput platforms, as well as uniform guidelines for bioinformatic analyses.

Primary ex vivo cultures of human fallopian tube epithelium as a model for serous ovarian carcinogenesis

Recent studies suggest that some serous ovarian carcinomas (SOCs) arise from the fallopian tube (FT) epithelium rather than the ovarian surface epithelium. This hypothesis places emphasis on the FT secretory epithelial cell as a cell-of-origin. Herein, we report the development of a novel ex vivo primary human FT epithelium culture system that faithfully recapitulates the in vivo epithelium, as shown by morphological, ultrastructural and immunophenotypic analyses. Mass spectrometry-based proteomics reveal that these cultures secrete proteins previously identified as biomarkers for ovarian cancer. We also use this culture system to study the response of the FT epithelium to genotoxic stress and find that the secretory cells exhibit a distinct response to DNA damage when compared with neighboring ciliated cells. The secretory cells show a limited ability to resolve the damage over time, potentially leaving them more susceptible to accumulation of additional mutagenic injury. This divergent response is confirmed with in situ studies using tissue samples, further supporting the use of this ex vivo culture system to investigate FT epithelial pathobiology. We anticipate that this novel culture system will facilitate the study of SOC pathogenesis, and propose that similar culture systems could be developed for other organ site-specific epithelia.

Recent advances in molecular gynaecological pathology

This review gives an overview of recent advances in our understanding of the molecular basis of gynaecological malignancy, including cervical, vulval, endometrial and ovarian tumours. These advances are beginning to influence clinical practice, perhaps most notably with the introduction of human papillomavirus vaccination for the prevention of anogenital neoplasia, but are likely to have broader clinical implications as further details emerge.

Ovarian low-grade and high-grade serous carcinoma: pathogenesis, clinicopathologic and molecular biologic features, and diagnostic problems

Ovarian serous carcinomas have been graded using various systems. Recently, a 2-tier system in which tumors are subdivided into low grade and high grade has been proposed. This approach is simplistic, reproducible, and based on biologic evidence indicating that both tumors develop via different pathways. Low-grade serous carcinomas exhibit low-grade nuclei with infrequent mitotic figures. They evolve from adenofibromas or borderline tumors, have frequent mutations of the KRAS, BRAF, or ERBB2 genes, and lack TP53 mutations (Type I pathway). The progression to invasive carcinoma is a slow step-wise process. Low-grade tumors are indolent and have better outcome than high-grade tumors. In contrast, high-grade serous carcinomas have high-grade nuclei and numerous mitotic figures. Identification of a precursor lesion in the ovary has been elusive and therefore the origin of ovarian carcinoma has been described as de novo. More recently, studies have suggested that a proportion seem to originate from intraepithelial carcinoma in the fallopian tube. The development of these tumors is rapid (Type II pathway). Most are characterized by TP53 mutations and lack mutations of KRAS, BRAF, or ERBB2. Although both types of serous carcinomas evolve along different pathways, rare high-grade serous carcinomas seem to arise through the Type I pathway. Immunohistochemical stains for p53, p16, and Ki-67 for distinction of low-grade from high-grade tumors are of limited value but can be helpful in selected instances. This review provides an update on the pathogenesis and clinicopathologic features of these 2 types of serous carcinomas and addresses some of the diagnostic problems that are encountered in routine practice.

Rapidly increasing incidence of papillary serous carcinoma of the peritoneum in the United States: fact or artifact?

Papillary serous carcinoma of the peritoneum (PSCP) has been recognized for almost 5 decades, but little is known about the etiology or pathogenesis of this uncommon malignancy. The objective of this analysis was to examine trends in the incidence of PSCP in the United States. Invasive PSCP cases (N = 4,389) were identified through 24 population-based registries in the United States during the period 1995-2004. Incidence rates were calculated per million population. PSCP is a disease of older women, with few cases diagnosed before the age of 40 years. The incidence of PSCP was 64% lower among black women and 47% lower among Asian-Pacific Islander women compared with white women. Rates among Hispanic women were 39% lower than among non-Hispanic women. The majority of PSCP (68%) was diagnosed at a distant stage, underscoring the difficulty of diagnosing this malignancy. The incidence of PSCP has increased dramatically during the past decade in the United States with the greatest rise (>13% per year) among non-Hispanic and white women. This trend was more pronounced among older women and women with early stage disease. The incidence of PSCP shows substantial racial and ethnic diversity. The increase in the rate of PSCP among all racial and ethnic groups during the 10-year observation period is cause for some alarm. Although the reason for this temporal trend is unknown, some of the increase may be attributable to reclassification of ovarian carcinoma to the peritoneum.

Incidence of ovarian, peritoneal, and fallopian tube carcinomas in the United States, 1995-2004

OBJECTIVE

The objective of this analysis was to describe the distribution of pelvic carcinomas in the United States by demographic, pathologic, and clinical features.

METHODS

Carcinomas of the ovary (n = 112,541), peritoneum (n = 6,458), and fallopian tube (n = 3,479) were identified through 24 population-based registries in the United States during the period 1995 to 2004. Age-adjusted incidence rates were calculated per million population using counts derived from the 2000 U.S. census.

RESULTS

The age-adjusted incidence rate for ovarian carcinoma (119.9 per million) was substantially higher than for peritoneal (6.78 per million) or fallopian tube (3.72 per million) carcinomas. White women had the highest rates for all three malignancies. Rates for peritoneal carcinoma were lowest among Black women (2.88 per million) and rates for fallopian tube carcinoma were lowest among Hispanic women (2.45 per million). Serous carcinomas were the most commonly diagnosed histologic type for all anatomic sites. Peritoneal carcinomas were diagnosed at later ages (mean, 67 years) and more advanced stages (85% regional/distant) compared with fallopian tube carcinomas (mean, 64 years; 62% regional/distant) and ovarian carcinomas (mean, 63 years; 76% regional/distant). Incidence for all three pelvic carcinomas was lowest in the South. Time trend analyses between 1973 and 2005 exhibited a significant decline in ovarian carcinoma incidence and rises in the rates of peritoneal and fallopian tube cancers.

CONCLUSIONS

Similarities in the incidence patterns for ovarian, peritoneal, and fallopian tube carcinomas support the likelihood of a common molecular pathogenesis.

Hereditary ovarian carcinoma: heterogeneity, molecular genetics, pathology, and management

Hereditary ovarian cancer accounts for at least 5% of the estimated 22,000 new cases of this disease during 2009. During this same time, over 15,000 will die from malignancy ascribed to ovarian origin. The bulk of these hereditary cases fits the hereditary breast-ovarian cancer syndrome, while virtually all of the remainder will be consonant with the Lynch syndrome, disorders which are autosomal dominantly inherited. Advances in molecular genetics have led to the identification of BRCA1 and BRCA2 gene mutations which predispose to the hereditary breast-ovarian cancer syndrome, and mutations in mismatch repair genes, the most common of which are MSH2 and MLH1, which predispose to Lynch syndrome. These discoveries enable relatively certain diagnosis, limited only by their variable penetrance, so that identification of mutation carriers through a comprehensive cancer family history might be possible. This paper reviews the subject of hereditary ovarian cancer, with particular attention to its molecular genetic basis, its pathology, and its phenotypic/genotypic heterogeneity.

New insights into the pathogenesis of serous ovarian cancer and its clinical impact

There are only a handful of concepts concerning cancer and carcinogenesis that are currently beyond dispute. One such dogma is the adenoma-carcinoma sequence and that a multistep accumulation of genetic alterations is required for transformation from a benign to a neoplastic tissue. The inevitable derivative of this dogma is that every invasive carcinoma is in fact a missed intraepithelial tumor, and furthermore, a late evolutionary stage in the sequence of development from a precursor lesion. Until fairly recently, high-grade serous ovarian carcinoma seemed to be one of the only known deviants of these concepts. In this article, we discuss the emergence of the fallopian tube fimbria as a field of origin for high-grade serous carcinomas and present a binary model of ovarian cancer pathogenesis that takes into consideration prior epidemiologic, morphologic, and genetic data. With the rise of the fallopian tube secretory epithelial cell as a cell of origin for high-grade pelvic serous carcinomas, the need to develop tools and model systems to characterize the biology and physiology of this cell is recognized.