Evidence for a latent precursor (p53 signature) that may precede serous endometrial intraepithelial carcinoma

Special Considerations in Classification and Workup of Endometrial Carcinomas

CONTEXT.—

A variety of uncommon malignant endometrial tumors can be challenging to diagnose because of overlapping morphology with more common entities. In some cases, immunohistochemical stains and/or molecular testing allow for more definitive diagnosis or prognostication.

OBJECTIVE.—

To review classic morphologic features of uncommon endometrial tumors, pathologic features of these tumors and their mimics, and the evidence for use of immunohistochemistry and molecular testing in the diagnosis of these tumors.

DATA SOURCES.—

University of Michigan (Ann Arbor) cases and review of pertinent literature about each entity.

CONCLUSIONS.—

Although each of these uncommon endometrial tumors has morphologic mimics, key histologic features, immunohistochemical stains, and molecular testing allow for accurate classification.

Improving the Diagnosis of Endometrial Hyperplasia Using Computerized Analysis and Immunohistochemical Biomarkers

Endometrial hyperplasia (EH) is a precursor lesion to endometrial carcinoma (EC). Risks for EC include genetic, hormonal and metabolic factors most notably those associated with obesity: rates are rising and there is concern that cases in pre-menopausal women may remain undetected. Making an accurate distinction between benign and pre-malignant disease is both a challenge for the pathologist and important to the gynecologist who wants to deliver the most appropriate care to meet the needs of the patient. Premalignant change may be recognized by histological changes of endometrial hyperplasia (which may occur with or without atypia) and endometrial intraepithelial neoplasia (EIN). In this study we created a tissue resource of EH samples diagnosed between 2004 and 2009 (n = 125) and used this to address key questions: 1. Are the EIN/WHO2014 diagnostic criteria able to consistently identify premalignant endometrium? 2. Can computer aided image analysis inform identification of EIN? 3. Can we improve diagnosis by incorporating analysis of protein expression using immunohistochemistry. Our findings confirmed the inclusion of EIN in diagnostic criteria resulted in a better agreement between expert pathologists compared with the previous WHO94 criteria used for the original diagnosis of our sample set. A computer model based on assessment of stromal:epithelial ratio appeared most accurate in classification of areas of tissue without EIN. From an extensive panel of putative endometrial protein tissue biomarkers a score based on assessment of HAND2, PTEN, and PAX2 was able to identify four clusters one of which appeared to be more likely to be benign. In summary, our study has highlighted new opportunities to improve diagnosis of pre-malignant disease in endometrium and provide a platform for further research on this important topic.

Molecular catastrophe, the peritoneal cavity and ovarian cancer prevention

The current theory of carcinogenesis for the deadliest of "ovarian" cancers - high-grade serous carcinoma (HGSC) - holds that the malignancy develops first in the fallopian tube and spreads to the ovaries, peritoneum and/or regional lymph nodes. This is based primarily on the observation of early forms of serous neoplasia (serous tubular intraepithelial lesions (STILs), and serous tubular intraepithelial carcinomas (STICS)) in the fimbria of women undergoing risk reduction surgery. However, these lesions are uncommon in the general population, confer a low risk (5%) of HGSC following their removal in at-risk women with germ-line BRCA1/2 mutations and require 4 or more years to recur as intraperitoneal HGSC. These features suggest that isolated STILs and STICs behave as precursors with uncertain cancer risk rather than carcinomas. Their evolution to HGSC after escape from the tube could proceed step-wise with multiple biologic events; however, it is unclear whether immediately adjacent HGSCs in the setting of advanced disease evolved in the same fashion. The latter scenario could also be explained by a "catastrophic" model in which STICs suddenly develop with invasive and metastatic potential, overwhelming or obscuring the site of origin. Moreover, a similar model might explain the sudden emergence of HGSC in the peritoneal cavity following escape of precursor cells years before. Long term follow-up data from opportunistic or prophylactic salpingectomy should shed light on where malignant transformation occurs, as well as the time-line from precursor to metastatic HGSC. This article is protected by copyright. All rights reserved.

Endometrial cancer

Although endometrial cancer management remains challenging, a deeper understanding of the genetic diversity as well as the drivers of the various pathogenic states of this disease has led to development of divergent management approaches in an effort to improve therapeutic precision in this complex malignancy. This comprehensive review provides an update on the epidemiology, pathophysiology, diagnosis and molecular classification, recent advancements in disease management, as well as important patient quality-of-life considerations and emerging developments in the rapidly evolving therapeutic landscape of endometrial cancers.

High-grade endometrial carcinomas: Morphologic spectrum and molecular classification

High-grade endometrial carcinoma (HGEC) is a heterogeneous group of tumors with various morphologic, genetic, and clinical characteristics. Morphologically, HGEC includes high-grade endometrioid carcinoma, serous carcinoma, clear cell carcinoma, undifferentiated/dedifferentiated carcinoma, and carcinosarcoma. The morphologic classification has been used for prognostication and treatment decisions. However, patient management based on morphologic classification is limited by suboptimal interobserver reproducibility, variable clinical outcomes observed within the same histotype, and frequent discordant histotyping/grading between biopsy and hysterectomy specimens. Recent studies from The Cancer Genome Atlas (TCGA) Research Network established four distinct molecular subtypes: POLE-ultramutated, microsatellite unstable, copy number high, and copy number low groups. Compared to histotyping, the TCGA molecular classification appears superior in risk stratification. The best prognosis is seen in the POLE-ultramutated group and the worst in copy number high group, while the prognosis in the microsatellite unstable and copy number low groups is in between. The TCGA subtyping is more reproducible and shows a better concordance between endometrial biopsy and resection specimens. It has now become apparent that the molecular classification can supplement histotyping in patient management. This article provides an overview of the pathologic diagnosis/differential diagnosis of HGEC and the TCGA classification of endometrial cancers, with the clinical significance and applications of TCGA classification briefly discussed when appropriate.

Exploring the clinical significance of serous tubal intraepithelial carcinoma associated with advanced high-grade serous ovarian cancer: A Memorial Sloan Kettering Team Ovary Study

OBJECTIVE

To evaluate the clinical significance and genomic associations of concurrent serous tubal intraepithelial carcinoma (STIC) with high-grade serous carcinoma (HGSC) of the ovary in women undergoing primary debulking surgery (PDS).

METHODS

All patients who underwent PDS for HGSC between 01/2015 and 12/2018 were captured in a prospectively maintained institutional database. Patients were categorized based on the presence or absence of concurrent STIC noted on final pathology. Demographic, perioperative, and outcomes data were collected, and groups were compared using standard statistical tests. Progression-free survival (PFS) and overall survival (OS) were evaluated using the Kaplan-Meier method. For comparison of differences in somatic alterations between the two cohorts, specimens were sequenced using MSK-IMPACT.

RESULTS

Of 306 eligible patients, 87 (28%) had a concurrent STIC lesion (+STIC) and 219 (72%) did not (no-STIC). Demographics and clinicopathological factors were similar between the two cohorts, except for a significantly higher median preoperative CA-125 level in the no-STIC group (423 U/mL vs. 321 U/mL; p=0.029). There were no significant differences in median PFS (22.7 months [95%CI: 18.9-28.4] vs. 27.7 months [95%CI: 25.5-30.5]; p=0.126) and 3- year OS rate (81% [95%CI: 70-88%] vs. 85% [95%CI: 78-90%]; p=0.392) between +STIC and no-STIC patients, respectively. Targeted DNA-sequencing via MSK-IMPACT showed a similar distribution of driver mutations or structural genetic alterations, and affected genetic signaling pathways were similar between the cohorts.

CONCLUSIONS

There were no identifiable clinical and genetic differences in patients with HGSC and concurrent STIC. These data suggest a comparable, if not identical, disease process.

Integrative Transcriptome Analyses of the Human Fallopian Tube: Fimbria and Ampulla-Site of Origin of Serous Carcinoma of the Ovary

Epithelial ovarian cancer represents a group of heterogeneous diseases with high grade serous cancer (HGSC) representing the most common histotype. Molecular profiles of precancerous lesions found in the fallopian tube have implicated this tissue as the presumptive site of origin of HGSC. Precancerous lesions are primarily found in the distal fallopian tube (fimbria), near the ovary relative to the proximal tissue (ampulla), nearer to the uterus. The proximity of the fimbria to the ovary and the link between ovulation, through follicular fluid release, and ovarian cancer risk led us to examine transcriptional responses of fallopian tube epithelia (FTE) at the different anatomical sites of the human fallopian tube. Gene expression profiles of matched FTE from the fimbria and from premenopausal women resulted in differentially expressed genes (DEGs): CYYR1, SALL1, FOXP2, TAAR1, AKR1C2/C3/C4, NMBR, ME1 and GSTA2. These genes are part of the antioxidant, stem and inflammation pathways. Comparisons between the luteal phase (post-ovulation) to the follicular phase (pre-ovulation) demonstrated greater differences in DEGs than a comparison between fimbria and fallopian tube anatomical differences alone. This data suggests that cyclical transcriptional changes experienced in pre-menopause are inherent physiological triggers that expose the FTE in the fimbria to cytotoxic stressors. These cyclical exposures induce transcriptional changes reflective of genotoxic and cytotoxic damage to the FTE in the fimbria which are closely related to transcriptional and genomic alterations observed in ovarian cancer.

[Precursor lesions of endometrial carcinoma]

The 2014 WHO classification distinguishes between endometrial hyperplasia without atypia (EH) and atypical endometrial hyperplasia/endometrioid intraepithelial neoplasia (AEH/EIN). AEH/EIN is characterized by crowded glands with cytologically atypical epithelium separated by little intervening stroma. Cellular atypia is characterized by nuclear enlargement and rounding, pleomorphism, loss of polarity, and presence of nucleoli. The diagnosis of atypia is facilitated by comparison with areas of adjacent normal and non-atypical glands, respectively. AEH/EIN is often associated with squamous but also secretory and mucinous metaplasia. Loss of PTEN and/or PAX2 immunoreactivity occurs in up to two thirds of AEH/EIN. In contrast, invasive low-grade endometrioid carcinoma shows confluent growth with loss of stroma and formation of labyrinth-like or cribriform structures. Differential diagnosis includes different forms of metaplasias, papillary proliferations, and hyperplastic polyps. Epithelial metaplasia may be present in various benign endometrial lesions as well as in endometrioid adenocarcinoma. AEH/EIN may also occur in endometrial polyps. Progestin therapy of AEH/EIN has low level of evidence but frequently leads to complete regression. Serous intraepithelial carcinoma (SEIC) is characterized by high-grade cellular atypia and polymorphism, detachment of cells, a mutant immunoreactive pattern for the P53 and an increased Ki67 labeling index. Although designated as precursor of serous carcinoma of the endometrium, biologically it is considered a non-invasive serous carcinoma since it may already be associated with massive extrauterine spread.

The fallopian tube, "precursor escape" and narrowing the knowledge gap to the origins of high-grade serous carcinoma

Most ovarian carcinomas are high-grade serous carcinomas (HGSC) that contain TP53 mutations, present at advanced stage, and eventually become resistant to chemotherapy. The rapid evolution of this disease has been attributed to an origin in the distal fallopian tube, in the form of serous tubal intraepithelial carcinomas (STICs). This has led to a disease model where malignancy develops first in the tube and spreads to the peritoneum or regional lymph nodes. However, although most early or incidentally discovered HGSCs manifest in the tube with STICs, many advanced HGSCs are not accompanied by a malignancy in the fimbria. To resolve this paradox, the focus has shifted to earlier, premalignant serous proliferations (ESPs) in the tubes, which lack the cytomorphologic features of malignancy but contain TP53 mutations. These have been termed p53 signatures or serous tubal intraepithelial lesions (STILs). Although they have not been presumed to have cancer-causing potential by themselves, some ESPs have recently been shown to share identical TP53 mutations with concurrent HGSCs, indicating a shared lineage between these early mucosal changes and metastatic malignancy. This discovery supports a paradigm by which HGSCs can emerge not only from STICs but also from exfoliated precursor cells (precursor escape) that eventually undergo malignant transformation within the peritoneal cavity. This paradigm unifies both localized and widespread HGSCs to a visible pre-existing cellular alteration in the tubal epithelium, and highlights a consistent and necessary biologic event (TP53 mutation) rarely encountered in the ovary or secondary Mullerian system. This dual pathway to HGSCs underscores the subtle nature of many serous cancer origins in the tube, explains contrasting clinico-pathologic presentations, and explains why, until recently, the fallopian tube was unappreciated as the principal origin of HGSCs. Moreover, it highlights additional challenges faced in preventing or intercepting HGSCs at a curable stage.

Back to the Future? The Fallopian Tube, Precursor Escape and a Dualistic Model of High-Grade Serous Carcinogenesis

Beginning with the discovery of the BRCA-associated ovarian cancer susceptibility genes and subsequent detailed examination of risk-reducing salpingo-oophorectomy (RRSO) specimens, a new paradigm of ovarian carcinogenesis has unfolded with attention to the distal fallopian tube. The primary focus has been an early cancer or neoplasm in the fallopian tube which is seen in virtually all incidentally discovered high-grade serous cancers in asymptomatic women. This high-frequency of tubal involvement in early serous neoplasm (usually in the form of serous tubal intraepithelial carcinoma—STIC) has galvanized attention to this organ as a primary source of this disease. However, an enduring mystery has been the relatively low frequency of STIC in the fallopian tubes of women with advanced malignancy. This paradox, a high frequency of tubal involvement early on and a low frequency of involvement later in the disease process, has spurred interest in other potential sources, such as the ovarian surface epithelium or cortical inclusions and the secondary Mullerian system. However, because essentially all high-grade serous carcinomas are linked by TP53 mutations, and because fallopian tubes frequently contain early serous proliferations (ESPs) with these mutations, attention has turned to the possibility that the nonmalignant but TP53 mutated tubal epithelium could be responsible for an eventual malignancy. Recent data have shown evidence of a lineage continuity between ESPs and concurrent serous carcinomas prompting the concept of “precursor escape”. This creates a second component of the paradigm by which cells from early precursors are shed from the tube and undergo subsequent malignant transformation, emerging suddenly as widespread intraperitoneal malignancy. This dualistic model thus provides a unique pathway by which the future outcome (wide spread high-grade serous carcinomas—HGSC) is ultimately explained by going back in time to an early serous proliferation. This paradigm also brings the peritoneal cavity into focus, raising new questions about the potential co-variables or exposures that might facilitate the occasional malignant transformation of an ESP in the peritoneal cavity or on the peritoneal surface.

Evidence for lineage continuity between early serous proliferations (ESPs) in the Fallopian tube and disseminated high-grade serous carcinomas

The distal Fallopian tube is a site of origin for many 'ovarian' high-grade serous carcinomas (HGSCs) with intraepithelial carcinomas (STICs) that share identical TP53 mutations with metastatic tumors. TP53 mutation-positive early serous proliferations (ESPs) comprise a spectrum including p53 signatures and serous tubal intraepithelial lesions (STILs) and are not considered malignant; however, ESPs are often the only abnormality found in Fallopian tubes of women with metastatic HGSC. The purpose of this study was to determine if a relationship exists between isolated ESPs and concurrent metastatic HGSCs in the absence of STIC. Fallopian tubes from 32 HGSCs without a co-existing STIC/HGSC in the endosalpinx were exhaustively sectioned. The presence of either STIC/HGSC or ESP in the endosalpinx was documented and DNA from tissues containing ESPs, concurrent HGSC, and control epithelia were interrogated for TP53 mutations by targeted amplicon-based sequencing with average coverage reads >4000 across DNA replicate samples. Serial sectioning revealed a previously unrecognized STIC/HGSC in 3 of 32 (9.3%) and ESPs in 13 (40.6%). Twelve contained TP53 mutations. Nine (75%) shared identical TP53 mutations with concurrent HGSCs, four at high (≥ 5%) and five at low (< 5%) allele frequency. All control epithelia were TP53 mutation-negative. This study, for the first time, indicates lineage identity between ESPs in the distal tube and some metastatic HGSCs via a shared site-specific TP53 mutation. It supports a novel serous carcinogenic sequence in which an ESP could eventually culminate in a metastatic serous cancer via 'precursor escape' and would explain the apparent sudden onset of cancers without co-existing STICs. This paradigm for serous cancer development underscores the likelihood that multiple precursor types in the Fallopian tube contribute to serous cancer development with implications for the evolution, pathologic classification, and prevention of this lethal malignancy. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Concomitant p53 and PTEN immunoexpression to predict the risk of malignancy in endometrial polyps

The aim of this retrospective cross-sectional study was to assess the usefulness of phosphase and tensin homolog deleted on chromosome 10 (PTEN) and p53 protein immunoexpression in predicting the risk of malignancy in endometrial polyps. The study was conducted at tertiary public hospital, university teaching center, and private practice clinic.A total of 159 patients with endometrial polyps who underwent hysteroscopic polypectomy between January 2010 to December 2014 were included. p53 and PTEN immunoexpression were assessed in histologic endometrial polyp samples. Patients were allocated into 2 groups: group A, endometrial polyps without atypia (120), and group B, endometrial polyps with atypia (39), which were subdivided into A1 (80) and B1 (21) = p53-/PTEN+ immunostaining; A2 (20) and B2 (11) = p53+/PTEN+; A3 (14) and B3 (4) = p53+/PTEN-; A4 (6) and B4 (3) = p53-/PTEN-.There was no significant difference between groups regarding clinical and epidemiologic parameters, except for age. Neoplasia incidence within groups was higher when at least 1 marker was abnormally stained (in group A, P = .0089, odds ratio [OR] = 13.94 [1.62; 120.27]; in group B, P = .0255, OR 12.73 [1.38; 117.27]). Overall neoplasia incidence was higher in group B than in group A (20.5% vs 5.8%; P = .0113). Malignant neoplasia was found more frequently in patients with p53+ (P = .0006, OR = 7.67 [2.30; 25.54]) and PTEN- (P = .0043; OR = 5.43 [1.77; 16.61]).Immunohistochemical analysis using p53 and PTEN as markers, either alone or concomitantly, can be useful to predict malignant transformation in cases of endometrial polyps.

Does a p53 "Wild-type" Immunophenotype Exclude a Diagnosis of Endometrial Serous Carcinoma?

An aberrant p53 immunophenotype may be identified in several histotypes of endometrial carcinoma, and is accordingly recognized to lack diagnostic specificity in and of itself. However, based on the high frequency with which p53 aberrations have historically been identified in endometrial serous carcinoma, a mutation-type immunophenotype is considered to be highly sensitive for the histotype. Using an illustrative case study and a review of the literature, we explore a relatively routine diagnostic question: whether the negative predictive value of a wild-type p53 immunophenotype for serous carcinoma is absolute, that is, whether a p53-wild type immunophenotype is absolutely incompatible with a diagnosis of serous carcinoma. The case is an advanced stage endometrial carcinoma that was reproducibly classified by pathologists from 3 institutions as serous carcinoma based on its morphologic features. By immunohistochemistry, the tumor was p53-wild type (DO-7 clone), diffusely positive for p16 (block positivity), and showed retained expression of PTEN, MSH2, MSH6, MLH1, and PMS2. Next generation sequencing showed that there indeed was an underlying mutation in TP53 (D393fs*78, R213*). The tumor was microsatellite stable, had a low mutational burden (4 mutations per MB), and displayed no mutations in the exonuclease domain of DNA polymerase epsilon (POLE) gene. Other genomic alterations included RB1 mutation (R46fs*19), amplifications in MYST3 and CRKL, and ARID1A deletion (splice site 5125-94_5138del108). A review of the recent literature identified 5 studies in which a total of 259 cases of serous carcinoma were whole-exome sequenced. The average TP53 mutational rate in endometrial serous carcinoma was only 75% (range, 60 to 88). A total of 12 (33%) of 36 immunohistochemical studies reported a p53-aberrant rate of <80% in endometrial serous carcinoma. We discuss in detail several potential explanations that may underlie the scenario of serous carcinoma-like morphology combined with p53-wild-type immunophenotype, including analytic limitations, a nonserous histotype displaying morphologic mimicry of serous carcinoma, and true biological phenomena (including the possibility of a TP53-independent pathway of endometrial serous carcinogenesis). Ultimately, our central thematic question is provisionally answered in the negative. At present, the available data would not support a categorical conclusion that a p53 alteration is a necessary and obligate component in the genesis and/or diagnosis of endometrial serous carcinoma. On the basis of their collective experience, the authors proffer some recommendations on the use of p53 immunohistochemistry in the histotyping of endometrial carcinomas.

Practical issues in the diagnosis of serous carcinoma of the endometrium

Serous carcinoma (SC) represents ~10% of endometrial carcinomas, but is responsible for almost 40% of cancer deaths. This article reviews the main pathological features, differential diagnosis, and the usefulness of molecular pathology and immunohistochemistry in its diagnosis. Most helpful features for the diagnosis include: irregularly shaped and sized papillae, slit-like spaces, cell stratification and budding, highly atypical cells, architectural and cytological discordance in pseudoglandular tumors, as well as lack of endometrioid features. SC shows typically a predominant papillary growth, which is also found in some subtypes of endometrioid carcinoma of the endometrium (EEC). Distinction is easy when attention is paid to the presence of diffuse marked nuclear pleomorphism, but also to the complex papillary architecture. SC may also show a solid or pseudoglandular patterns, and in these cases differential diagnosis may be difficult with EEC grade 3. Moreover, a high proportion of SC may exhibit clear cells, and, thus, may be confused with clear cell carcinoma. Finally, it is sometimes difficult to distinguish mixed SC-EEC, from SC that combines papillary and pseudoglandular growths. Although there is not a single immunohistochemical marker for distinguishing SC from its mimickers, some antibodies are useful (p53, p16, IMP2, and IMP3), particularly when used in combination. Diagnosis of SC may be even more problematic in small biopsies; a diagnosis of high-grade endometrial carcinoma, SC component can not be excluded, is acceptable as a managerial approach, so it could be taken into account at the time of final surgery.

Characterization of precursor lesions in the endometrium and fallopian tube epithelium of early-stage uterine serous carcinoma

To determine if selected cases of uterine serous carcinoma (USC) arise from tubal rather than endometrial epithelium. Bilateral fallopian tubes from 38 women with pure USC were entirely submitted for histopathologic examination using the protocol Sectioning and Extensively Examining the FIMbria (SEE-FIM). Non-neoplastic endometrium was extensively sampled. Immunohistochemistry for p53 was performed on all paraffin blocks of fallopian tube and non-neoplastic endometrium. Endometrial intraepithelial carcinoma (EIC) was present in 22 cases (58%). Endometrial p53 foci were identified in 3 patients. There were 11 cases (29%) with fallopian tube involvement; 9 of 11 had tubal wall invasion or lymphatic involvement without serous tubal intraepithelial carcinoma (STIC) and were, therefore, classified as metastatic from the endometrium. STIC was identified in 3 patients (8%). There were 3 cases with tubal p53 foci in non-neoplastic epithelium. EIC was present in 58% of patients, further supporting EIC as a precursor lesion to USC. STIC was present in 8%, suggesting that the fallopian tube may in fact represent the primary lesion in a minority of patients with USC. This finding may account for the early multifocal disease distribution observed in these patients.

Overexpression of p53 in the endometrial gland in postmenopausal women

OBJECTIVE

The p53 signature, which (although morphologically unremarkable) displays diffuse and strong p53 nuclear staining, has been proposed to be a precursor of serous endometrial intraepithelial carcinoma. We examined the overexpression of p53 in postmenopausal endometrial glands.

METHODS

Postmenopausal endometrial tissues of 82 women with benign disease, including 10 hormone users, were evaluated in this study. Tissues with endometrial hyperplasia and/or polyps were excluded based on a histopathologic review. Expressions of estrogen receptor-α, Ki-67, and p53 were immunohistochemically examined. Apoptotic cells were identified using a terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Overexpression of p53 was categorized as moderate to strong in more than 50% of glandular cell nuclei.

RESULTS

Focal glandular overexpression of p53 was observed in 1 (9%) of 10 and in 8 (11%) of 72 postmenopausal endometrial tissue specimens in women with and women without a history of hormone use, respectively. Among nonhormone users, the median Ki-67 and apoptotic indices in the postmenopausal endometrial glands of women with and women without overexpression of p53 were 16% and 6% (P = 0.007) and 1% and 1% (P = 0.345), respectively. All postmenopausal endometrial glands were positive for estrogen receptor-α, regardless of the overexpression of p53. The postmenopausal endometrial glands of estrogen users exhibited significantly higher Ki-67 and apoptotic indices than those of nonestrogen users (P = 0.001 and P < 0.001, respectively).

CONCLUSIONS

Overexpression of p53 may be responsible for the high proliferative activity of postmenopausal endometrial glandular cells associated with conditions of low apoptotic cell death.

Significance of p53 expression in background endometrium in endometrial carcinoma

The p53 signature (p53S) has been proposed to be a marker of the earliest phase of development of endometrial serous carcinoma. We examined the presence of p53S in the background endometrium in cases of endometrial carcinoma. From a series of 351 endometrial carcinomas, 225 (64.1 %) lesions, for which slides of the adjacent noncancerous endometrium were available for review, were included. Expression of estrogen receptor (ER)-alpha, Ki-67, and p53 in the adjacent endometrium was studied by immunohistochemistry. The p53S was defined as the presence of morphologically benign endometrial epithelial cells with moderate to strong intensity of p53 immunostaining. Of the 225 noncancerous endometrium samples, 34 consisted of hyperplastic and 191 of non-hyperplastic endometrium. A p53S was found in 22 cases (mean age 64.2 years), 2 in hyperplastic, and 20 in non-hyperplastic background endometrium. All p53S-positive cases also expressed ER-alpha; their median Ki-67 labeling index (LI) was 4.0 % (range 0.0 to 21.0 %). The two cases with hyperplastic p53S-positive background endometrium were in association with a grade 1 endometrioid tumor in a premenopausal woman with Lynch syndrome. Of the 152 cases of endometrioid adenocarcinomas with non-hyperplastic endometrium, 12 (8 %) were p53S positive, none of which associated with EIC. Of the 21 cases of serous carcinoma, five (24 %) were p53S positive, 4 of which (19 %) associated with EIC while in 5 others (24 %) EIC was found without p53S. Of three clear cell adenocarcinomas, none were p53S positive while two contained EIC without p53S. Of 15 carcinosarcomas, 3 (20 %) were p53S positive, all of which with EIC while 6 others (40 %) were associated with EIC but without p53S. Of the 8 non-endometrioid tumors with p53S, 7 (88 %) were associated with EIC. p53S is thought to be associated with precancerous lesions of non-endometrioid tumors, including carcinosarcomas.

A genetically engineered ovarian cancer mouse model based on fallopian tube transformation mimics human high-grade serous carcinoma development

Recent evidence suggests that ovarian high-grade serous carcinoma (HGSC) originates from the epithelium of the fallopian tube. However, most mouse models are based on the previous prevailing view that ovarian cancer develops from the transformation of the ovarian surface epithelium. Here, we report the extensive histological and molecular characterization of the mogp-TAg transgenic mouse, which expresses the SV40 large T-antigen (TAg) under the control of the mouse müllerian-specific Ovgp-1 promoter. Histological analysis of the fallopian tubes of mogp-TAg mice identified a variety of neoplastic lesions analogous to those described as precursors to ovarian HGSC. We identified areas of normal-appearing p53-positive epithelium that are similar to 'p53 signatures' in the human fallopian tube. More advanced proliferative lesions with nuclear atypia and epithelial stratification were also identified that were morphologically and immunohistochemically reminiscent of human serous tubal intraepithelial carcinoma (STIC), a potential precursor of ovarian HGSC. Beside these non-invasive precursor lesions, we also identified invasive adenocarcinoma in the ovaries of 56% of the mice. Microarray analysis revealed several genes differentially expressed between the fallopian tube of mogp-TAg and wild-type (WT) C57BL/6. One of these genes, Top2a, which encodes topoisomerase IIα, was shown by immunohistochemistry to be concurrently expressed with elevated p53 and was specifically elevated in mouse STICs but not in the surrounding tissues. TOP2A protein was also found elevated in human STICs, low-grade and high-grade serous carcinoma. The mouse model reported here displays a progression from normal tubal epithelium to invasive HGSC in the ovary, and therefore closely simulates the current emerging model of human ovarian HGSC pathogenesis. This mouse therefore has the potential to be a very useful new model for elucidating the mechanisms of serous ovarian tumourigenesis, as well as for developing novel approaches for the prevention, diagnosis and therapy of this disease.

[p53 suppresses type II endometrial carcinomas in mice and governs endometrial tumor aggressiveness in humans]

Type II endometrial carcinomas are a highly aggressive group of tumor subtypes that are frequently associated with inactivation of the TP53 tumor suppressor gene. We show that mice with endometrium-specific deletion of the Trp53 gene initially exhibited histological changes that are identical to known precursor lesions of type II endometrial carcinomas in humans and later developed carcinomas representing all type II subtypes. The mTORC1 signalling pathway was frequently activated in these precursor lesions and tumors, suggesting a genetic cooperation between this pathway and Trp53 deficiency in tumor initiation. Consistent with this idea, analyses of 521 human endometrial carcinomas identified frequent mTORC1 pathway activation in type I as well as type II endometrial carcinoma subtypes. The mTORC1 pathway activation and p53 expression or mutation status each independently predicted poor patient survival. We suggest that molecular alterations in p53 and the mTORC1 pathway play different roles in the initiation of the different endometrial cancer subtypes but combined p53 inactivation and mTORC1 pathway activation are unifying pathogenic features among histologically diverse subtypes of late stage aggressive endometrial tumors.

Family history and BRCA1/BRCA2 status among Japanese ovarian cancer patients and occult cancer in a BRCA1 mutant case

BACKGROUND

This study aimed to examine family history among Japanese ovarian cancer patients and to investigate the TP53 status of fallopian tube epithelial and ovarian cancer cells in a Japanese BRCA1 mutant case that may be associated with the transformed state in hereditary ovarian cancer.

METHODS

One hundred and two primary ovarian cancer patients were retrospectively evaluated in this cross-sectional study. The family history of cancer was determined in probands. In a BRCA1 mutant case, p53 immunostaining and direct sequencing, followed by laser-capture microdissection, were performed for the fallopian tube, considered the origin of ovarian cancer.

RESULTS

Nine of 102 (8.8%) families were regarded as having hereditary breast-ovarian cancer syndrome, two families (2.0%) were diagnosed with Lynch syndrome and six patients harbored BRCA1 or BRCA2 mutations. One case underwent risk-reductive salpingo-oophorectomy as a BRCA1 mutant carrier was retrospectively diagnosed as occult cancer. Common TP53 mutations were detected in cancer and fallopian tube epithelial cells in the case.

CONCLUSIONS

Here, we integrate family cancer history and histology in ovarian cancer cases as well as TP53 status in a BRCA1 mutant case into a discussion regarding carcinogenesis in a Japanese population. The TP53 status for the BRCA1 mutant case examined here supports the recently proposed theory that ovarian cancer develops because of BRCA1 or BRCA2 inactivation and/or TP53 mutations.

Type I to type II ovarian carcinoma progression: mutant Trp53 or Pik3ca confers a more aggressive tumor phenotype in a mouse model of ovarian cancer

A dualistic pathway model of ovarian carcinoma (OvCA) pathogenesis has been proposed: type I OvCAs are low grade, genetically stable, and relatively more indolent than type II OvCAs, most of which are high-grade serous carcinomas. Endometrioid OvCA (EOC) is a prototypical type I tumor, often harboring mutations that affect the Wnt and phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin signaling pathways. Molecular and histopathologic analyses indicate type I and II OvCAs share overlapping features, and a subset of EOCs may undergo type I→type II progression accompanied by acquisition of somatic TP53 or PIK3CA mutations. We used a murine model of EOC initiated by conditional inactivation of the Apc and Pten tumor suppressor genes to investigate mutant Trp53 or Pik3ca alleles as key drivers of type I→type II OvCA progression. In the mouse EOC model, the presence of somatic Trp53 or Pik3ca mutations resulted in shortened survival and more widespread metastasis. Activation of mutant Pik3ca alone had no demonstrable effect on the ovarian surface epithelium but resulted in papillary hyperplasia when coupled with Pten inactivation. Our findings indicate that the adverse prognosis associated with TP53 and PIK3CA mutations in human cancers can be functionally replicated in mouse models of type I→type II OvCA progression. Moreover, the models should represent a robust platform for assessment of the contributions of Trp53 or Pik3ca defects in the response of EOCs to conventional and targeted drugs.

γH2AX as a marker of DNA double strand breaks and genomic instability in human population studies

DNA double strand breaks (DSB) are the gravest form of DNA damage in eukaryotic cells. Failure to detect DSB and activate appropriate DNA damage responses can cause genomic instability, leading to tumorigenesis and possibly accelerated aging. Phosphorylated histone H2AX (γH2AX) is used as a biomarker of cellular response to DSB and its potential for monitoring DNA damage and repair in human populations has been explored in this review. A systematic search was conducted in PubMed for articles, in English, on human studies reporting γH2AX as a biomarker of either DNA repair or DNA damage. A total of 68 publications were identified. Thirty-four studies (50.0%) evaluated the effect of medical procedures or treatments on γH2AX levels; 20 (29.4%) monitored γH2AX in specific pathological conditions with a case/control or case/case design; 5 studies (7.4%) evaluated the effect of environmental genotoxic exposures, and 9 (13.2%) were descriptive studies on cancer and aging. Peripheral blood lymphocytes (44.6%) or biopsies/tissue specimens (24.3%) were the most commonly used samples. γH2AX was scored by optical microscopy as immunostained foci (78%), or by flow cytometry (16%). Critical features affecting the reliability of the assay, including protocols heterogeneity, specimen, cell cycle, kinetics, study design, and statistical analysis, are hereby discussed. Because of its sensitivity, efficiency and mechanistic relevance, the γH2AX assay has great potential as a DNA damage biomarker; however, the technical and epidemiological heterogeneity highlighted in this review infer a necessity for experimental standardization of the assay.

p53 suppresses type II endometrial carcinomas in mice and governs endometrial tumour aggressiveness in humans

Type II endometrial carcinomas are a highly aggressive group of tumour subtypes that are frequently associated with inactivation of the TP53 tumour suppressor gene. We show that mice with endometrium-specific deletion of Trp53 initially exhibited histological changes that are identical to known precursor lesions of type II endometrial carcinomas in humans and later developed carcinomas representing all type II subtypes. The mTORC1 signalling pathway was frequently activated in these precursor lesions and tumours, suggesting a genetic cooperation between this pathway and Trp53 deficiency in tumour initiation. Consistent with this idea, analyses of 521 human endometrial carcinomas identified frequent mTORC1 pathway activation in type I as well as type II endometrial carcinoma subtypes. mTORC1 pathway activation and p53 expression or mutation status each independently predicted poor patient survival. We suggest that molecular alterations in p53 and the mTORC1 pathway play different roles in the initiation of the different endometrial cancer subtypes, but that combined p53 inactivation and mTORC1 pathway activation are unifying pathogenic features among histologically diverse subtypes of late stage aggressive endometrial tumours.

A case of serous endometrial intraepithelial carcinoma with p53 positivity for six years

A 69-year-old postmenopausal woman was referred because she had been taking tamoxifen for four years. Tissues obtained by endometrial curettage were immunopositive for p53, but there was no definite malignancy. At age 73, cytology again showed abnormalities, so we repeated complete endometrial curettage. Again, there was no malignancy, but p53 immunostaining was widely positive. At age 75, hysterectomy was performed because cytological examination showed increasingly abnormal findings and the patient opted for surgery. In the resected uterus, endometrial glands were replaced by malignant cells resembling papillary serous carcinoma cells with high-grade nuclei, but there was no stromal or myometrial invasion. The pathological diagnosis was intraepithelial serous endometrial carcinoma. This is a rare case because we could follow the patient for 6 years by endometrial cytology or endometrial curettage and we observed gradual transformation into endometrial intraepithelial carcinoma.

Evaluating the progenitor cells of ovarian cancer: analysis of current animal models

Serous ovarian cancer is one of the most lethal gynecological malignancies. Progress on effective diagnostics and therapeutics for this disease are hampered by ambiguity as to the cellular origins of this histotype of ovarian cancer, as well as limited suitable animal models to analyze early stages of disease. In this report, we will review current animal models with respect to the two proposed progenitor cells for serous ovarian cancer, the ovarian surface epithelium and the fallopian tube epithelium.

[Precursor lesions of endometrial carcinoma: diagnostic approach and molecular pathology]

For endometrial adenocarcinoma two precursor lesions are known: endometrioid adenocarcinoma which is the most frequent type 1 carcinoma develops from atypical endometrial hyperplasia whereas endometrial intraepithelial carcinoma (EIC) is the precursor of serous carcinoma and a subset of clear cell carcinoma both representing type 2 carcinomas. Atypical hyperplasia which shows progression rates into carcinoma of up to 40% is challenged by its poor interobserver reproducibility. A better reproducibility is obtained by the endometrial intraepithelial neoplasia (EIN) concept with fewer categories but it is not compatible with the World Health Organization (WHO) classification of endometrial hyperplasia. The EIN concept includes not only the vast majority of the WHO atypical hyperplasia but also approximately half of the complex hyperplasia without atypia. Rarely, atypical hyperplasia is associated with a secretory or mucinous cell type and two thirds of atypical hyperplasia resolve under long-term high dosage progestin therapy. Immunohistochemistry aids in the differential diagnosis of atypical hyperplasia and EIC. Atypical hyperplasia/EIN frequently show PTEN and/or Pax-2 negativity and low Ki-67 and differ from EIC which shows strong diffuse p53 staining and high Ki-67 staining index.

High frequency of PIK3R1 and PIK3R2 mutations in endometrial cancer elucidates a novel mechanism for regulation of PTEN protein stability

We demonstrate that phosphatidylinositol 3-kinase (PI3K) pathway aberrations occur in >80% of endometrioid endometrial cancers, with coordinate mutations of multiple PI3K pathway members being more common than predicted by chance. PIK3R1 (p85α) mutations occur at a higher rate in endometrial cancer than in any other tumor lineage, and PIK3R2 (p85β), not previously demonstrated to be a cancer gene, is also frequently mutated. The dominant activation event in the PI3K pathway appears to be PTEN protein loss. However, in tumors with retained PTEN protein, PI3K pathway mutations phenocopy PTEN loss, resulting in pathway activation. KRAS mutations are common in endometrioid tumors activating independent events from PI3K pathway aberrations. Multiple PIK3R1 and PIK3R2 mutations demonstrate gain of function, including disruption of a novel mechanism of pathway regulation wherein p85α dimers bind and stabilize PTEN. Taken together, the PI3K pathway represents a critical driver of endometrial cancer pathogenesis and a novel therapeutic target.

Atypical Endometrial Hyperplasia and Well Differentiated Endometrioid Adenocarcinoma of the Uterine Corpus

The distinction between atypical endometrial hyperplasia and well differentiated adenocarcinoma of the endometrium is one of the more difficult differential diagnoses in gynecologic pathology. Different pathologists apply different histologic criteria, often with different individual thresholds for atypical endometrial hyperplasia and grade 1 adenocarcinoma. While some classifications are based on a series of molecular genetic alterations (which may or may not translate into biologically or clinically relevant risk lesions), almost all current diagnostic criteria use a series of histologic features - usually a combination of architecture and cytology - for diagnosing atypical hyperplasia and adenocarcinoma. This article presents evidence-based histologic criteria for atypical endometrial hyperplasia and low grade endometrial carcinoma (both FIGO grade 1 and 2) with emphasis on common and not so common histologic mimics. Grade 3 endometrioid carcinoma is discussed in the Oliva and Soslow article in this publication.

Personal history of breast cancer as a significant risk factor for endometrial serous carcinoma in women aged 55 years old or younger

A comparative study between endometrial serous carcinoma (ESC) and endometrial endometrioid carcinoma (EEC) was performed to determine whether a personal history of breast cancer is a risk factor for ESC in women aged ≤ 55 yr. Study subjects consisted of 348 women who were diagnosed with ESC and 830 comparison subjects who had EEC. Variables studied included age at diagnosis, a history of breast cancer, tamoxifen therapy, hormonal replacement therapy and smoking history. Overall, 19.4% of women with ESC had a history of breast cancer, which was significantly higher than that of 3% in comparison subjects. Among the study subjects, the incidence of a prior breast cancer was significantly higher in patients who were 55 yr of age or younger (41.5%) than those who were older than 55 yr (16%). The statistical significance of both of the aforementioned comparisons was independent of tamoxifen usage on multivariate analyses. The mean time interval between prior breast cancer and endometrial cancer was 92.5 mo (range 7-240 mo) in the study group and 79 mo (range 7-192 mo) in the comparison group. For the whole cohort and individual subgroups (ESC, EEC, ≤ 55 yr and >55 yr), a personal history of breast cancer did not adversely affect the patient outcomes, which was largely dependent on standard clinicopathologic parameters such as International Federation of Gynecology and Obstetrics stage, as has previously been demonstrated. These findings suggest that a personal history of breast cancer may be a significant risk factor for the development of ESC in women aged ≤ 55 yr. Further studies are needed to clarify the relationship between these two cancers in this age group and whether this increased risk is reflective of a genetic predisposition.

Microscopic and early-stage ovarian cancers in BRCA1/2 mutation carriers: building a model for early BRCA-associated tumorigenesis

Risk-reducing salpingo-oophorectomy (RRSO) is the cornerstone of ovarian cancer prevention in BRCA1/2 mutation carriers. Occult fallopian tube and ovarian cancers have been reported in a small percentage of BRCA1/2 mutation carriers undergoing RRSO. Here, we review our single-institution experience with RRSO in BRCA1/2 mutation carriers to characterize cases of microscopic cancers in these patients. At the time of RRSO, 7.9% of BRCA1 mutation carriers were diagnosed with microscopic fallopian tube or ovarian cancers and no cases were diagnosed in BRCA2 mutation carriers. The majority of the microscopic cancers include cases that were confined to the fallopian tubes, although there were also cases involving ovaries only or peritoneal washings only. This suggests that the site of origin may be in the ovary, fallopian tube, or peritoneum for BRCA-associated serous cancers. However, an analysis of early-stage (stages I and II) ovarian and fallopian tube cancers diagnosed in BRCA1/2 mutation carriers confirms that the ovary is a preferred site for tumor growth with 11 of 14 early-stage cancers having a dominant ovarian mass. Overall, these data suggest that cancer initiation may occur in the ovary, fallopian tube, or peritoneum, but tumor growth and progression are favored in the ovary. We present an updated model for BRCA1/2 mutation-associated ovarian and fallopian tube carcinogenesis, which may aid in identifying improved prevention strategies for high-risk women who delay or decline RRSO.

[Serous genital carcinoma: molecular pathogenesis and the role of tubal fimbria]

Serous carcinomas develop at various sites of the Mullerian system, in particular, the ovaries, the peritoneum, the uterus and the fallopian tubes. Currently, two distinctive molecular genetic pathways are distinguished for serous tumorigenesis: type I tumors are typically well differentiated and gradually develop from cystadenoma through borderline tumor to low grade carcinoma and are characterized by B-raf and K-ras mutations, whereas the poorly differentiated type II tumors develop from intraepithelial carcinoma and show p53 mutations. Infrequently, p53 mutations occur as a late event in the type I pathway and lead to a high grade tumor phenotype. A histologically inconspicuous possible precursor lesion of the intraepithelial carcinoma is the p53 signature that shows p53 overexpression without cell cycle deregulation. Whereas in the ovaries both pathways may occur and develop from inclusions of the surface epithelium, the fallopian tube has recently been described as an important site for the type II pathway. High grade serous carcinomas and intraepithelial carcinomas of the tubal fimbria are particularly found in patients with BRCA1/BRCA2 germ line mutations. Since an advanced tumor stage is frequent and often makes the determination of the origin impossible, the term pelvic serous carcinoma was recently proposed for high grade serous (adeno)carcinomas involving multiple sites.

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.

p53 overexpression in morphologically ambiguous endometrial carcinomas correlates with adverse clinical outcomes

The distinction between uterine serous and endometrioid carcinomas can usually be achieved by morphologic examination alone. However, there are occasional 'morphologically ambiguous endometrial carcinomas' that show overlapping serous and endometrioid features and defy histologic classification. The primary aim of this study was to assess the clinical significance of p53 overexpression using immunohistochemistry in such tumors. Related aims included (1) assessing interobserver diagnostic concordance for histologic subclassification of these tumors using a panel of pathologists with and without gynecologic pathology expertise and (2) elucidating the histologic features that correlate with p53 status. Thirty-five such cases were identified during the study period. p53 overexpression was seen in 17 of 35 cases. Tumors with p53 overexpression were associated with a significantly inferior progression-free survival and disease-specific survival compared with those that lacked p53 overexpression (3-year progression-free survival and disease-specific survival were 94 and 100% in patients with no p53 overexpression, and 52 and 54% in patients with p53 overexpression; P=0.02 and 0.003, respectively). The consensus diagnosis rendered by gynecologic pathologists was predictive of disease-specific survival (P=0.002), but not progression-free survival (P=0.11). Although the interobserver diagnostic concordance (kappa=0.70) was substantial for gynecologic pathologists, and highly associated with p53 status (77% of 'favor serous' cases showed p53 overexpression, whereas only 25% of 'favor endometrioid' cases showed p53 overexpression; P=0.005), the concordance between the consensus diagnosis of the two specialized pathologists versus each of three non-specialized pathologists was poor (kappa=0.13-0.25). The histologic feature that correlated most with p53 overexpression was the presence of diffuse high nuclear grade. p53 immunohistochemistry assays in morphologically ambiguous endometrial carcinomas are roughly as clinically informative as gynecologic pathology consultation and can be helpful for prognostic assessment and therapeutic decision making in difficult endometrial carcinomas.