Sporadic microsatellite instability is specific to neoplastic and preneoplastic endometrial tissues

Nuclear Beta-Catenin Expression in Endometrioid Intraepithelial Neoplasia (Atypical Hyperplasia) Does Not Predict Carcinoma on Subsequent Hysterectomy

Beta-catenin (BC) mutations are associated with a high risk of recurrence in otherwise low-grade, early-stage uterine endometrioid adenocarcinomas. Recent literature suggests nuclear BC expression by immunohistochemistry is highly sensitive and specific for BC mutations. The significance of BC expression in endometrioid intraepithelial neoplasia (EIN/atypical hyperplasia) and its relationship to altered differentiation patterns in EIN has yet to be fully explored. Cases meeting current diagnostic criteria for EIN based on H&E examination were obtained from 2 institutions (years 1999-2014). Patterns of altered differentiation (eg, tubal, squamous morular metaplasia, mucinous, secretory) were noted. Representative blocks were stained for BC, and expression patterns recorded. Follow-up and demographic data was obtained from the electronic medical record. Ninety-six cases were included (84 biopsies, 12 hysterectomies). BC nuclear expression was identified in 41 cases (42.7%), with 33 of 41 demonstrating foci of nonmorular BC staining. BC staining in any component of EIN was not significantly associated with the presence of carcinoma on subsequent hysterectomy (P=0.79). When restricting to nonmorular BC, the results were the same (P=0.56). Cases with tubal differentiation were significantly less likely to demonstrate nonmorular BC than cases with no specific pattern of differentiation (P<0.01). EIN frequently demonstrates BC nuclear positivity, especially in cases without tubal differentiation. BC nuclear expression in EIN does not appear to be associated with an increased likelihood of carcinoma on subsequent hysterectomy. Our results do not support routine use of BC immunohistochemistry as a prognostic biomarker in cases of EIN.

Gynaecological neoplasms in common familial syndromes (Lynch and HBOC)

Recognising hereditary predisposition in a cancer patient has implications both for the patient and the patient's kindred. For the latter, cascade germline testing can reassure those not-at-risk family members while carriers can be enrolled in cancer screening and prevention programs that are medically effective and economically sustainable for health care systems. Furthermore, in many of these syndromes, ramifications of molecular phenotypes are increasing, and it is now emerging that, in addition, they convey prognostic and predictive information. Although cancer predisposition syndromes are rare, these molecular phenotypes also occur as somatic events in sporadic cancer settings. The information obtained from these molecular phenotypes, regardless of germline or somatic origin, is being incorporated into clinical management in view of their manifold significance. Thus, increasingly, bespoke management of cancer patients involves testing for both germline and somatic mutations in tumours. Lynch syndrome and BRCA-1 and BRCA-2-associated hereditary breast and ovarian cancer are hereditary cancer syndromes frequently involving the gynaecological tract but tumours associated with similar molecular alterations may also occur sporadically. Thus, the molecular phenotype of mismatch repair deficiency, microsatellite instability or hypermutator phenotype may be attributable to germline or somatic events. Similarly, homologous recombination deficiency or 'BRCAness' in ovarian cancers may be syndromic or sporadic. While hereditary syndromes are well recognised, the prognostic and predictive implications of these molecular phenotypes have only recently been elucidated and these aspects will finally ensure that molecular screening may become standard of care. Thus, nowadays pathologists are asked to designate the molecular phenotype of these cancers and then determine whether it is due to hereditary or sporadic causes.

Emergence, involution, and progression to carcinoma of mutant clones in normal endometrial tissues

Sporadic somatic inactivation of genes such as PTEN within histologically normal endometrium (latent precancers) is an early step in endometrial carcinogenesis. We have used clone-specific mutations of PTEN to determine the fate of latent precancers over time in women who do (high risk) and do not (low risk) develop endometrial neoplasia. PTEN immunohistochemistry was performed on 45 occurrences of endometrial neoplasia and their paired antecedent benign biopsies, along with age matched sample pairs from 167 patients who did not develop a neoplasm. When PTEN-deficient cells were present at both time points, DNA sequencing was performed to determine whether they were single or multiple independent events. Loss of PTEN protein in isolated glands was common in the initial normal biopsies of high- and low-risk groups (42% and 27%, respectively, P = 0.066). Protein-deficient glands have a tendency to disappear over time in low-risk women (P = 0.047) and, even when "persistent," are infrequently (19%, 3/16) confirmed to be the same clone. Similarly, only a small proportion (6.7%, 1/15) of latent precancers seen in high-risk women are the direct progenitors of subsequent neoplasia. There is a high rate of latent precancer turnover in both low- and high-risk patients, with rare long-term persistence of unique clones, which may or may not progress to a histologic lesion. The temporal dynamics of clonal emergence, persistence, and involution are sufficiently complex that in the individual patient, the presence of a latent precancer has an unknown contribution to long-term cancer risk.

Targeted endometrial cancer therapy as a future prospect

Among female-specific cancers worldwide, endometrial cancer is the third most common after breast cancer and cervical cancer. In addition, it is the most common gynecological cancer in the USA and Europe. The incidence of this disease appears to be increasing. The cause of this increase is multifactorial, but a few possible factors involved are increasing obesity, an aging population leading to more postmenopausal women and greater tamoxifen use. Surgery is generally the primary treatment of this disease and postoperative radiation therapy in some patients with high or intermediate risk may prevent locoregional recurrences. Adjuvant chemotherapy improves progression-free survival in advanced or recurrent cancer. However, overall survival in patients with advanced disease is poor. Hence, better therapy is needed and targeted molecular therapies are emerging as possible treatment candidates. These include molecules that target VEGF, mTOR, tyrosine kinases, human EGF receptors and FGF receptors. Therapies targeting specific molecular features should be evaluated in future strategies in the treatment of endometrial cancer.

Malignant tumors of the female reproductive system

This review summarizes the epidemiology of cancer of the female reproductive system and associated lifestyle factors. It also assesses the available evidence for occupational factors associated with these cancers. Cervical, endometrial, and ovarian cancers are relatively common, and cause significant cancer morbidity and mortality worldwide, whereas vulvar, vaginal, fallopian tube cancers, and choriocarcinomas are very rare. As several lifestyle factors are known to play a major role in the etiology of these cancers, very few published studies have investigated possible relationships with occupational factors. Some occupational exposures have been associated with increased risks of these cancers, but apart from the available evidence on the relationships between asbestos fibers and ovarian cancer, and tetrachloroethylene and cervical cancer, the data is rather scarce. Given the multifactorial nature of cancers of the female reproductive system, it is of the utmost importance to conduct occupational studies that will gather detailed data on potential individual confounding factors, in particular reproductive history and other factors that influence the body's hormonal environment, together with information on socio-economic status and lifestyle factors, including physical activity from multiple sources. Studies on the mechanisms of carcinogenesis in the female reproductive organs are also needed in order to elucidate the possible role of chemical exposures in the development of these cancers.

Microsatellite instability in endometrial polyps

OBJECTIVE(S)

To investigate the prevalence of microsatellite instability (MSI) in endometrial polyps and to evaluate whether there are clinical and histopathological parameters associated with this kind of instability.

STUDY DESIGN

Between September 2008 and April 2009, endometrial polyps were collected from 109 patients. MSI was evaluated using the NCI recommended markers BAT25, BAT26, D2S123, D5S346 and D17S250. Histopathological analysis was performed, and clinical information was obtained from patients' records.

RESULT(S)

MSI low was detected in 6.4% of the validated samples (7/109). Of the seven MSI that were detected, six were positive for instability at D17S250 and one at D5S346. There were no significant differences between polyps with or without MSI with regard to age, BMI, menarche, parity, miscarriage or menopause; however, MSI was more frequent in polyps with simple hyperplasia without atypia (3/20; 15%). Furthermore, patients with multiple polyps had a marginally but statistically insignificant increase in the frequency of MSI (p<0.07).

CONCLUSION(S)

This is the first prospective study of MSI in endometrial polyps using hysteroscopically obtained samples. In a population of 109 patients, MSI was infrequent in endometrial polyps. Although MSI appears to be more frequent in multiple polyps and polyps with simple hyperplasia without atypia, this was not statistically significant.

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.

Molecular analysis of endometrial tumorigenesis: importance of complex hyperplasia regardless of atypia

PURPOSE

Endometrial carcinoma (EC) is common in the population and the most frequent extracolonic malignancy in hereditary nonpolyposis colorectal carcinoma (HNPCC)/Lynch syndrome. We characterized precursor lesions of endometrioid EC to identify markers of malignant transformation and tumor progression.

EXPERIMENTAL DESIGN

Serial specimens of normal endometrium, simple hyperplasia, complex hyperplasia without atypia, complex hyperplasia with atypia, and endometrial carcinoma obtained during a 10-year surveillance of DNA mismatch repair (MMR) gene mutation carriers (together 110 samples) were molecularly profiled and compared with a sporadic reference series of endometrial specimens taken for nonmalignant reasons (62 samples).

RESULTS

Among MMR gene mutation carriers, decreased MMR protein expression was present in 7% in normal endometrium, 40% in simple hyperplasia, 100% in complex hyperplasia without atypia, 92% in complex hyperplasia with atypia, and 100% in endometrial carcinoma. Microsatellite instability frequencies were lower (6%, 17%, 67%, 38%, and 64%, respectively). Among 24 tumor suppressor genes, the number of methylated loci increased from normal endometrium to simple hyperplasia to complex hyperplasia (complex hyperplasia without atypia/complex hyperplasia with atypia) in both Lynch syndrome and reference series. The most frequently methylated genes were CDH13, RASSF1A, and GSTP1. In MMR gene mutation carriers, MMR and methylation defects appeared up to 12 years before endometrial carcinoma.

CONCLUSIONS

Molecular changes in endometrial tissue are detectable several years before endometrial carcinoma in genetically predisposed individuals. Abnormal MMR and methylation classify normal endometrium and simple hyperplasia into one category and complex hyperplasia without atypia, complex hyperplasia with atypia, and endometrial carcinoma into another, suggesting that, contrary to a traditional view, complex hyperplasia without atypia and complex hyperplasia with atypia are equally important as precursor lesions of endometrial carcinoma.

Molecular and Pathologic Aspects of Endometrial Carcinogenesis

Endometrial cancer is the most common gynecological malignancy, with 41,000 new cases projected in the United States for 2006. Two different clinicopathologic subtypes are recognized: the estrogen-related (type I, endometrioid) and the non–estrogen-related types (type II, nonendometrioid such as papillary serous and clear cell). The morphologic differences in these cancers are mirrored in their molecular genetic profile with type I showing defects in DNA-mismatch repair and mutations in PTEN, K-ras, and beta-catenin, and type II showing aneuploidy and p53 mutations. This article reviews the genetic aspects of endometrial carcinogenesis and progression. We will define the precursor lesion of type I endometrioid cancer and the role of genetics and estrogen in its progression.

The relationship between microsatellite instability and PTEN gene mutations in endometrial cancer

Microsatellite instability (MSI) and mutations in the PTEN gene are among the molecular alterations involved in endometrial carcinogenesis. There is conflicting information regarding to their role in this type of tumor. For this reason, we have studied both molecular lesions in a large population-based series of 205 patients with sporadic endometrial cancer. MSI was found in 41 (20.0%) of the tumors and PTEN mutations were found in 74 (36.1%). There were differences in genotype between tumors with and without MSI. Tumors with MSI showed both a higher frequency of PTEN mutations (58.5% vs. 30.4%) (p=0.002, Fisher's exact test) and a higher number of insertions or deletions (I/D) of one nucleotide within the mononucleotide tracts of the PTEN gene (45.8% vs. 11.4% out of all I/D, p=0.005). Conversely, G:C to A:T transitions in CpG dinucleotides were found mostly in microsatellite stable tumors (57.7% vs. 18.2% out of all single-base substitutions, p=0.037). Overall, 67.6% of tumors with mutated PTEN exhibited multiple mutations or allelic imbalance (AI). Multiple PTEN mutations in the same tumor were more frequent in tumors with MSI (60% vs. 25.7%); by contrast the presence of AI accompanying PTEN mutation was higher in microsatellite stable tumors (74.3% vs. 40%) (p=0.028). In addition, patients with both genetic alterations were diagnosed at more advanced stage of progression (54.2% for MSI vs. 20.0% for MSS, p=0.006), and exhibited a worse prognosis (hazard ratio [95% confidence interval]: 3.0 [1.1-13.1], p=0.034, log-rank test) than patients with only the PTEN gene mutated. Our data suggest that the DNA mismatch repair system status influences: (i) both the frequency and the mutational spectrum of PTEN; (ii) the nature of one of the hits that inactivate this tumor-suppressor gene; and (iii) the clinical condition and behavior of the patients.

Microsatellite instability in endometrioid endometrial carcinoma: correlation with clinically relevant pathologic variables

This study of 218 patients with endometrioid endometrial carcinoma explores the relationship between microsatellite instability (MSI) as established by the BAT26 method and the common pathologic variables of prognostic and therapeutic significance. MSI was positively correlated with grade, associated endometrial atrophy, squamous metaplasia, isthmic involvement, depth of myoinvasion, vascular invasion-associated changes, extrauterine tumor spread, and extramyometrial angiolymphatic spread. There was no significant correlation with carcinoma developing in adenomyosis, mucinous metaplasia, tumor size, cornual involvement, cervical extension, uterine serosal involvement, and targeted lymphoid response. The positive correlations are discussed in terms of molecular genetics.

Genetic derangements in the tumor suppressor gene PTEN in endometrial precancers as prognostic markers for cancer development: a population-based study from northern Norway with long-term follow-up

OBJECTIVES

The purpose of the current study was to characterize the role of PTEN in malignant transformation and to evaluate the significance of mutated PTEN exons as prognostic markers in the carcinogenesis of endometrial hyperplasia. A comparison of PTEN mutations as prognostic markers with former investigated prognosticators was also intended.

METHODS

Histological material from 68 patients with endometrial hyperplasia and 10-20 years of follow-up of whom 18 later developed cancer was examined. PCR amplification and DNA sequencing were performed, screening the most frequently mutated exons 5a-8b of the PTEN gene.

RESULTS

Mutations were demonstrated in 13.2% of the patients. Of the patients with cancer development, five showed to have PTEN mutations corresponding to 28%. Of the patients remaining without carcinoma, only 8% had PTEN mutations (P = 0.04). In total, there were three missense, three nonsense, and four frameshift mutations, and twice as many mutations leading to a truncated protein (six) than mutations altering one amino acid in the entire protein (three). Mutations were distributed in the following manner: three in exon 5a, two in exon 5b, two in exon 6, two in exon 7, and one in exon 8b. Only mutations in exons 6, 7, and 8a were connected with cancer development or coexisting cancer and six out of seven mutations within these exons were frameshift or nonsense mutations.

CONCLUSIONS

Our results showed that mutations in the PTEN gene were statistically more frequent in cases with cancer development or coexisting cancer. Although the specificity was acceptable, the sensitivity of PTEN mutations was too low to make it suitable as a tumor marker (sensitivity of 27% and specificity of 91%) in clinical practice.

Defective mismatch repair and the development of recurrent endometrial carcinoma

OBJECTIVE

To investigate whether defective DNA mismatch repair (MMR) defines a subgroup at risk for recurrence in sporadic endometrial carcinoma patients.

METHODS

Primary tumors from 44 patients with recurrent stage I endometrial carcinoma were compared after matching, with tumors of 44 patients being free of recurrence for minimal 3 years. Paraffin-embedded primary tumors (n = 88) and recurrent tumors (n = 32) were subjected to immunohistochemical analysis for hMSH2 and hMLH1 expression. Subsequently, a staining index (SI = 0-9) was calculated based on staining intensity and quantity. DNA was extracted from paraffin-embedded tissues, and promoter methylation of hMLH1 was determined by nested methylation-specific PCR (MSP). Microsatellite instability (MSI) was assessed by BAT-26 or BAT-25.

RESULTS

Low hMSH2 expression was observed in 2% of primary tumors of control patients without recurrence, 14% of primary tumors of patients with recurrence, and 0% of recurrent tumors. Low hMLH1 expression was observed in 32%, 19%, and 22%, respectively. hMLH1 gene promoter methylation was detected in 50%, 47%, and 32%, and MSI was found in 16%, 14%, and 30%, respectively. No significant differences were found between primary tumors of patients with and without recurrence with respect to hMSH2 and hMLH1 expression, hMLH1 promoter methylation, and MSI. When primary and recurrent tumors were compared, there was an increased correlation of hMLH1 methylation with low hMLH1 expression and MSI in recurrent tumors.

CONCLUSION

MSI, hMLH1 promoter methylation, and the expression of hMLH1 and hMSH2 are not predictive for the development of recurrent stage I endometrial carcinoma. In the progression of tumor, "de novo" hMLH1 methylation rarely occurs, instead there is further derailment of the MMR pathway in affected tumors.

Correlation between the DNA global methylation status and progesterone receptor expression in normal endometrium, endometrioid adenocarcinoma and precursors

Endometrial carcinomas are the most common malignancy of the female genital tract and the third most common cancer in women. Progesterone and oestrogen receptors (PRs, ERs) are the most widely documented prognostic and predictive factors in endometrioid adenocarcinoma. Besides the hormonal pathway involved in the progression of preneoplastic and neoplastic lesions, alterations of the DNA methylation status have been shown to be an early signal of tumorigenesis. In this study, we show that in normal endometrium, during the proliferative phase, DNA methylation and PR expression are high, with a significant decline towards the end of the secretory phase and a gradual increase in non-atypical and atypical endometrial hyperplasia; they reach their highest level in grade I, then decrease significantly in grade-II and grade-III endometrioid adenocarcinomas. During each stage, a significant positive correlation is observed between DNA methylation and PR (P<0.0001). The strong parallelism between DNA methylation and PR expression precludes establishing a precise determination regarding the timing of these events, clearly involved in the genesis of endometrioid adenocarcinoma.

The postmenopausal ovary as an androgen-producing gland; hypothesis on the etiology of endometrial cancer

Postmenopausal estrogens originate from the peripheral conversion of androgens, which are produced by the adrenal glands and the ovaries. Estrogens are considered to contribute to the neoplastic development of endometrium. Hyperplasia of ovarian stroma is associated with an increased androgen production by the ovaries and with the development of endometrial pathology. We hypothesize that, in cases of endometrial pathology, an increased production of aromatizable androgens by postmenopausal ovaries will lead to elevated prehormone availability for estrogen formation in utero. Following the conversion of ovarian androgens, a reaction catalyzed by the cytochrome p450 aromatase, estrogens may function as a local mitogenic factor eventually leading to the development of endometrial cancer. We consider the local availability of androgens and the local activity of aromatase relevant for this process. If this hypothesis proves to be right it may give rise to the introduction of aromatase inhibitors in treatment strategies of hormone dependent endometrial malignancies.

PTEN mutations and evolving concepts in endometrial neoplasia

Several recent advances have been made in our understanding of the pathogenesis of endometrial tumours, particularly endometrioid endometrial carcinoma (EEC). Mutations in the PTEN gene and microsatellite instability (MSI) are common genetic abnormalities in EECs, and distinguish these lesions from other histological subtypes of endometrial carcinoma. Endometrial precancers are monoclonal lesions that share a common genetic lineage with invasive EEC, including PTEN mutations and MSI. Mutations of the PTEN tumour suppressor gene have been identified in histologically normal-appearing endometrium exposed to oestrogen, 18-55% of endometrial precancers and 26-80% of EECs. PTEN has been shown to play several roles in tumour suppression, including cell cycle arrest and promotion of apoptosis. Loss of PTEN function predisposes endometrial cells to neoplastic transformation, particularly in high-oestrogenic states. MSI is another common alteration seen in EECs and endometrial precancers, and some studies have reported an association between MSI and PTEN mutations. The replication error that results in MSI may facilitate the development of PTEN mutations in some, but not all, cases of EEC. The prognostic significance of PTEN gene mutations and MSI in endometrial carcinoma is controversial. Further study is needed to delineate the different pathogenetic pathways of EEC and their natural history.

Global expression changes of constitutive and hormonally regulated genes during endometrial neoplastic transformation

OBJECTIVE

Endometrioid endometrial carcinoma is caused by a combination of mutational events and hormonal factors. We used large-scale messenger RNA expression analysis to discover genes that distinguish neoplastic transformation and examine the patterns of tumor expression of those genes which are normally regulated during the menstrual cycle.

METHODS

Expression of approximately 6000 unique genes was quantified in 4 normal (2 proliferative, 2 secretory) and 10 malignant endometria using Affymetrix Hu6800 GeneChip probe arrays. Expression differences between normal and malignant tissue groups were measured by a test of statistical significance comparing the individual t statistic for each gene to the distribution of maximum t statistics among all genes following 1001 permutations of the tissue group assignments (Permax test). Hormonally responsive genes, selected by comparison of proliferative and secretory subsets of normal endometria using a combination of filters applied to the group means and t test rankings, were then examined in the tumors.

RESULTS

Fifty genes with a Permax <0.50 provided excellent discrimination between normal and malignant groups and were predominantly characterized by diminished expression levels in the cancers. We found that 100 genes which are hormonally regulated in normal tissues are expressed in a disordered and heterogeneous fashion in cancers, with tumors resembling proliferative more than secretory endometrium.

CONCLUSION

Neoplastic transformation is accompanied by predominant loss of activity of many genes constitutively expressed in normal source tissues and absence of expression profiles which characterize the antitumorigenic progestin response.

Atypical endometrial hyperplasia shares genomic abnormalities with endometrioid carcinoma by comparative genomic hybridization

Endometrial hyperplasia is a common disorder that is now observed with increasing frequency in women treated with hormonal replacement therapy or with tamoxifen. This study was undertaken to determine whether genomic features of various forms of endometrial hyperplasias would allow their classification as a benign, premalignant, or malignant abnormality. Comparative genomic hybridization (CGH) was performed on endometrial glands microdissected by laser capture microscope from 19 archival endometrial samples, comprising 5 normal endometria, 1 polyp, 2 simple hyperplasias, 5 hyperplasias with nuclear abnormalities (atypical hyperplasias), and 4 low-grade and 2 high-grade endometrioid carcinomas, 1 with squamous component (adenoacanthoma). Genomic DNA, extracted from the glands and the squamous component in 1 case, was amplified by degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR) and compared with sex-matched DNA by CGH. No genomic imbalances were observed in the normal samples, the polyp, or the simple hyperplasias. However, in atypical hyperplasia, regardless of the level of cytologic atypia, genomic abnormalities were observed that also occurred in endometrioid carcinomas. Chromosomes 1, 8, and 10 were most often affected. The results are compared with molecular genetic abnormalities recently reported in these lesions. This study strongly suggests that atypical endometrial hyperplasias are closely related to endometrioid carcinoma and should be considered precancerous lesions, contrary to simple hyperplasia, which is a benign disorder. The squamous component of one of the high-grade carcinomas showed genetic abnormalities similar to those of endometrioid carcinoma and therefore does not represent squamous metaplasia but is an integral part of the malignant process.

Histopathology of genetically defined endometrial precancers

Endometrial precancers are monoclonal, benign neoplasms prone to malignant transformation. A type collection (deposited at www.endometrium.org) of confirmed precancers has been identified by their monoclonal growth and continuity of acquired genetic markers that occur between premalignant and malignant phases of tumorigenesis. Computerized morphometry of these premalignant lesions, designated endometrial intraepithelial neoplasia (EIN), has disclosed new architectural criteria and revised cytologic criteria for their diagnosis. EIN lesions originate focally and expand in size over time, in keeping with a proliferative monoclonal origin. They are characterized by closely packed glands (volume percentage stroma < 55%) with cytology that is clearly demarcated from that of the adjacent field. A minimum homogeneous field of cytologically demarcated glands is required to accurately assess the architecture diagnostic of EIN, and morphometry-diagnosed lesions with a largest diameter of at least 1 to 2 mm have previously been shown to predict the relevant clinical outcome of concurrent or future endometrial adenocarcinoma. Nonphysiologic loss of the PTEN protein, a tumor suppressor gene mutated in many endometrioid adenocarcinomas, is seen in individual glands of endometrium exposed to unopposed estrogens and in packed clusters of EIN glands. The isolated PTEN-free glands in anovulatory endometria may be the earliest stage of endometrial tumorigenesis, but they are not readily distinguishable by routine histology, nor do they have a defined natural history.

Intratumoral genetic heterogeneity and progression of endometrioid type endometrial adenocarcinomas

OBJECTIVES

Development of genetic heterogeneity is one mechanism whereby tumors may acquire increasing aggressiveness during neoplastic progression. In this study we relate development of intratumoral genetic heterogeneity to invasion and metastatic spread of sporadic endometrioid (type I) endometrial adenocarcinomas.

METHODS

Microsatellite unstable adenocarcinomas underwent detailed microsatellite allelotype mapping with reconstruction of neoplastic lineages using maximum parsimony analysis.

RESULTS

Within individual patients, tumor allelotypes sometimes varied between regions of histologically identical tumor, indicating that genotypic variation may reflect differences inapparent by histology. Comparison of noninvasive (surface/luminal) with invasive (myometrial invasion or metastasis) carcinoma showed highly related genotypes in 3/8 cases in which the invasive component can be recognized as evolved from the superficial tumor lineage by progressive clonal selection. In 3/8 cases superficial and invasive genotypes independently evolved different sets of altered microsatellites, indicating either divergence at an early stage in tumor evolution or independent selection events. A total of 2/8 cases had random patterns of marker distribution between sampled areas that were not informative in delineating systematic relationships between surface and invasive tumor.

CONCLUSIONS

We conclude from these results that endometrial tumor progression may occur through physical extension of existing clones or through creation of new subclones with altered growth properties. The latter occurs in about half of cases, where myometrial invasion may select for particular clones that are poorly represented on the luminal surface.