Clonality analysis in synchronous or metachronous tumors of the female genital tract

Guidelines to Aid in the Distinction of Endometrial and Endocervical Carcinomas, and the Distinction of Independent Primary Carcinomas of the Endometrium and Adnexa From Metastatic Spread Between These and Other Sites

In most cases of suspected endometrial neoplasia tumor origin can be correctly assigned according to a combination of clinical, radiologic, and pathologic features, even when the latter are based upon the examination of relatively small biopsy samples. However there are well-recognized exceptions to this rule which continue to create diagnostic difficulty, and sometimes difficulties persist even after the detailed examination of resection specimens. Among the most common problems encountered in practice are the distinction of primary endometrial and primary endocervical adenocarcinomas, and the determination of tumor origin when there is synchronous, multifocal involvement of gynecologic tract sites, for example the endometrium and the ovary. However, accurate diagnosis in these cases is important because this has significant staging, management and prognostic implications. In this review we discuss the value and limitations of key morphologic, immunophenotypic and molecular findings in these diagnostic scenarios.

Potential for Mitochondrial DNA Sequencing in the Differential Diagnosis of Gynaecological Malignancies

In the event of multiple synchronous gynecological lesions, a fundamental piece of information to determine patient management, prognosis, and therapeutic regimen choice is whether the simultaneous malignancies arise independently or as a result of metastatic dissemination. An example of synchronous primary tumors of the female genital tract most frequently described are ovarian and endometrial cancers. Surgical findings and histopathological examination aimed at resolving this conundrum may be aided by molecular analyses, although they are too often inconclusive. High mitochondrial DNA (mtDNA) variability and its propensity to accumulate mutations has been proposed by our group as a tool to define clonality. We showed mtDNA sequencing to be informative in synchronous primary ovarian and endometrial cancer, detecting tumor-specific mutations in both lesions, ruling out independence of the two neoplasms, and indicating clonality. Furthermore, we tested this method in another frequent simultaneously detected gynecological lesion type, borderline ovarian cancer and their peritoneal implants, which may be monoclonal extra-ovarian metastases or polyclonal independent masses. The purpose of this review is to provide an update on the potential use of mtDNA sequencing in distinguishing independent and metastatic lesions in gynecological cancers, and to compare the efficiency of molecular analyses currently in use with this novel method.

Three primary synchronous malignancies of the uterus, cervix, and fallopian tube: A case report

RATIONALE

Multiple primary malignancies can occur in the same organ or in multiple organs or systems. Likewise, they can occur simultaneously or successively. Based on the timing of the diagnosis, they are classified as multiple synchronous (i.e., concurrent) or metachronous (i.e., successive) primary malignancies. The vast majority of patients have multiple metachronous malignant tumors; multiple synchronous tumors are rare.

PATIENT CONCERNS

A 63-year-old woman presented with the chief complaint of vaginal fluid discharge for 3 months and abdominal pain for 1 month.

DIAGNOSES

The patient was diagnosed with multiple synchronous primary malignancies: 1) endometrial poorly differentiated serous adenocarcinoma, stage IV; 2) poorly differentiated squamous cell carcinoma of the cervix, stage IB1; and 3) left-sided fallopian tube carcinoma in situ.

INTERVENTIONS

After total abdominal hysterectomy, bilateral salpingo-oophorectomy, and comprehensive staging and debulking, the patient was administered eight courses of adjuvant chemotherapy (taxane carboplatin/taxane cisplatin).

OUTCOMES

After chemotherapy completion, the patient has been undergoing regular follow-up examinations; no recurrence has been noted at 18 months.

LESSONS

It is important to distinguish between multiple synchronous primary malignancies and metastasis of a primary tumor to select the appropriate treatment regimen and to adequately assess the patient's prognosis. When a cancer patient shows clinical manifestations of another tumor, not only metastasis but also the possibility of multiple synchronous primary malignant tumors should be considered. The duration of follow-up in patients with malignant tumors should be extended as much as possible, as the timely detection and treatment of other primary malignant tumors can prolong survival and improve the quality of life.

Massively Parallel Sequencing-Based Clonality Analysis of Synchronous Endometrioid Endometrial and Ovarian Carcinomas

Synchronous early-stage endometrioid endometrial carcinomas (EECs) and endometrioid ovarian carcinomas (EOCs) are associated with a favorable prognosis and have been suggested to represent independent primary tumors rather than metastatic disease. We subjected sporadic synchronous EECs/EOCs from five patients to whole-exome massively parallel sequencing, which revealed that the EEC and EOC of each case displayed strikingly similar repertoires of somatic mutations and gene copy number alterations. Despite the presence of mutations restricted to the EEC or EOC in each case, we observed that the mutational processes that shaped their respective genomes were consistent. High-depth targeted massively parallel sequencing of sporadic synchronous EECs/EOCs from 17 additional patients confirmed that these lesions are clonally related. In an additional Lynch Syndrome case, however, the EEC and EOC were found to constitute independent cancers lacking somatic mutations in common. Taken together, sporadic synchronous EECs/EOCs are clonally related and likely constitute dissemination from one site to the other.

Copy number variants in clinical next-generation sequencing data can define the relationship between simultaneous tumors in an individual patient

Targeted next-generation sequencing (NGS) cancer panels have become a popular method for the identification of clinically predictive mutations in cancer. Such methods typically detect single nucleotide variants (SNVs) and small insertions/deletions (indels) in known cancer genes and can provide further information regarding diagnosis in challenging surgical pathology cases, as well as identify therapeutic targets and prognostically significant mutations. However, in addition to SNVs and indels, other mutation classes, including copy number variants (CNVs) and translocations, can be simultaneously detected from targeted NGS data. Here, as proof of methods, we present clinical data which demonstrate that targeted NGS panels can separate synchronous liver tumors based on CNV status, in the absence of distinct SNVs and indels. Such CNV-based analysis can be performed without additional cost using existing targeted cancer panel data and publically available software.

Triple Synchronous Primary Gynecologic Carcinomas

Double synchronous primaries are known to occasionally occur in gynecologic cancers. Cases of triple or quadruple synchronous primaries, with only 4 case reports in the literature, are extremely rare. The authors report the case of a 49-year-old para 2-0-0-2 woman who presented for surgical management of metastatic ovarian adenocarcinoma diagnosed at an outside institution. On examination of the surgical specimen, 3 synchronous primary carcinomas with multiple histologic features were identified within the ovaries, uterus, and cervix. Although rare, the possibility of triple synchronous primary malignancies should be considered when evaluating gynecologic malignancies.

Mitochondrial DNA genotyping reveals synchronous nature of simultaneously detected endometrial and ovarian cancers

Simultaneous independent primary tumors of the female genital tract occur in 1-2% of gynecological cancer patients, 50-70% of which are synchronous tumors of the endometrium and ovary. Guidelines for determining the nature of simultaneously detected tumors, based on surgical and histopathological findings, are often ambiguous and may require further molecular analyses. Such approach is necessary to indicate correct prognosis and hence treatment. We here demonstrate how mitochondrial DNA sequencing may provide a cheap and useful tool to contribute to indisputably recognize the synchronous nature of simultaneously detected endometrial and ovarian carcinomas. We further confirm our findings by means of Comparative Genomic Hybridization array analysis, which strengthens the informative potential of mitochondrial DNA genotyping in diagnosing synchrony.

Metastatic Neoplasms Involving the Ovary

In this review, ovarian metastatic carcinomas from various sites, as well as other neoplasms secondarily involving the ovary, are discussed. As well as describing the morphology, the value of immunohistochemistry in distinguishing between primary and metastatic neoplasms in the ovary is discussed. While immunohistochemistry has a valuable role to play and is paramount in some cases, the results should be interpreted with caution and with regard to the clinical picture and gross and microscopic pathologic findings.

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.

Four synchronous female genital malignancies: the ovary, cervix, endometrium and fallopian tube

OBJECTIVE

To present a unique case of a 63 year-old woman with coexistent adenocarcinoma of the ovary, endometrium, cervix and fallopian tube.

MATERIALS AND METHODS

A case report from a tertiary health center.

RESULTS

A woman presenting with postmenopausal bleeding and abdominal distantion was assessed by endometrial biopsy and explorative surgery. The frozen section of the mass on the right adnex revealed malign mucinous carcinoma of the ovary. As usual, optimal debulking was performed as initial surgical staging procedure of ovarian cancer. The microscopic examination of the right ovary revealed a typical mucinous cystadenocarcinoma. Furthermore, the focal endometrial irregularity at the left uterine cornus turned out to be a well differentiated endometrial carcinoma of the endometrioid type with <1/3 myometrial invasion. The pale infiltrative lesion in the cervix also turned out to be an adenocarcinoma of the endocervical type with deep stromal invasion and areas of diffuse glandular dysplasia and in-situ glandular neoplasia at the periphery. Besides, several sections from the left fallopian tube uncovered diffuse dysplasia in the lining epithelium and a focus of adenocarcinoma with papillary and cribriform pattern.

DISCUSSION

When compared with patients having metastatic lesions, most synchronous female malignancies are accompanied with early stage and low-grade with a more favorable prognosis. However, there is paucity of data for the exact criterion to distinguish primary tumors from metastatic lesions. In such cases, the validity of immunohistochemical and cloning studies are not clear.

Clinical analysis of synchronous primary neoplasms of the female reproductive tract

OBJECTIVES

In this study, a histopathologic review of synchronous primary neoplasms including gynecologic malignancies is presented, and the possible correlation among discrete tumor subsets, natural history, and survival is evaluated.

METHODS

Between the years 2000 and 2005, 20 patients suffering from synchronous primary cancers of gynecologic malignancy were identified. Clinical and pathologic information was obtained from medical records. Kaplan-Meier survival analyses were conducted.

RESULTS

Patients with synchronous primary malignancies constituted 0.63% of all genital malignancies. The most frequently observed synchronous neoplasm was ovarian cancer coexistent with endometrial cancer (40%). The mean age of patients suffering from synchronous ovarian and endometrial cancer was 45.2 years. All patients with synchronous primary genital malignancies underwent hysterectomy with bilateral salpingo-oophorectomy and/or adjuvant therapy. The mean duration of survival was 57 months (S.E.: 10.0; 95% confidence interval: 37-77).

CONCLUSION

Patients suffering from primary genital malignancies are sometimes co-afflicted with other primary cancers. Synchronous ovarian and endometrial cancer constitutes the most common of these cases, and is detected at a relatively early age, with generally favorable prognoses.

The high frequency of de novo promoter methylation in synchronous primary endometrial and ovarian carcinomas

PURPOSE

The methylation status of hMLH1, CDKN2A, and MGMT was investigated in a panel of synchronous cancers of the ovary and endometrium, fulfilling the clinicopathologic criteria for independent primary tumors to define the possible role of epigenetic mechanisms in the development of these cancers.

EXPERIMENTAL DESIGN

Bisulfite-converted DNA from 31 tumors (13 endometrial and 18 ovarian carcinomas) and from matched normal tissue of 13 patients was analyzed by a methylation-specific PCR assay at the CpG-rich 5' regions of all three genes. In all tumors, we also investigated the presence of microsatellite instability and hMLH1 immunohistochemical expression in relation to hMLH1 hypermethylation status.

RESULTS

Methylation of hMLH1, CDKN2A, and MGMT was detected in 39%, 41%, and 48% of endometrial and ovarian tumors, respectively. hMLH1 hypermethylation was observed in all tumors of five patients, and it was invariably associated with loss of hMLH1 protein and presence of microsatellite instability. CDKN2A and MGMT methylation was randomly detected among both endometrial (45% and 24% of cases, respectively) and ovarian carcinomas (39% and 39% of cases, respectively). Concordant methylation at two or three genes was observed in 35% of cases.

CONCLUSIONS

Epigenetic inactivation of hMLH1, CDKN2A, and MGMT may be a common and early event in the development of synchronous primary endometrial and ovarian carcinomas and may qualify as a marker of a field cancerization encompassing the ovary and endometrium. Detection of MGMT hypermethylation may be useful to define a set of gynecologic malignancies with a specific sensitivity to alkylating chemotherapy.

Molecular Genetic Evidence of an Independent Origin of Serous Low Malignant Potential Implants and Lymph Node Inclusions

Patients with ovarian serous tumors of low malignant potential (LMP) are commonly found to have peritoneal implants. Less commonly, similar lesions are seen in lymph nodes, sometimes in association with endosalpingiosis. We compared these lesions to the coexisting ovarian LMP tumors to determine whether they are clonally related to the ovarian neoplasm. Seventeen patients with serous LMP tumors present at 2 or more sites were identified. Tissue samples were microdissected from formalin-fixed paraffin-embedded tissue blocks. Samples of normal tissue, the ovarian LMP tumors, peritoneal LMP implants, and LMP inclusions within lymph nodes were obtained. Genomic DNA was extracted from the samples, and polymerase chain reaction and X-chromosome inactivation (human androgen receptor assay) analysis were performed. The pattern of X-chromosome inactivation could be determined in 15 of the 17 cases, and nonrandom X-chromosome inactivation was observed in 13 of these cases. Twelve of these cases included both ovarian and extraovarian LMP tumors. In 9 of these 12 cases, the extraovarian LMP tumor shared a similar pattern of nonrandom X-chromosome inactivation with the ovarian tumor. In these cases, the shared inactivation pattern was seen at 1 extraovarian site (3 cases), 2 extraovarian sites (4 cases), 5 extraovarian sites (1 case), and 7 of 8 extraovarian sites (1 case). In the remaining 3 cases, opposite patterns of nonrandom X-chromosome inactivation were seen. These data suggest that, in most cases, serous LMP tumor implants and lymph node inclusions share a common clonal origin with the associated ovarian tumors. However, in at least some cases, the implants and inclusions seem to arise independently from the associated ovarian serous LMP tumors.

Mucinous ovarian tumors associated with pseudomyxoma peritonei of adenomucinosis type: immunohistochemical evidence that they are secondary tumors

Pseudomyxoma peritonei (PMP) is a clinical condition initially thought to be related to ovarian mucinous tumors; however, immunohistochemistry and molecular biology techniques have convincingly made the link to appendiceal mucinous neoplasms, resulting in changes in histologic and clinical approaches. The objective of this study was to compare the immunohistochemical profile of ovarian tumors associated with PMP and intestinal mucinous ovarian neoplasms without PMP. The study was retrospective and included 28 intestinal ovarian mucinous tumors selected from the files of the Division of Surgical Pathology of the University of Sao Paulo Medical School, from 1996 to 2005. Seven cases were associated with PMP of disseminated peritoneal adenomucinosis-type and all presented borderline histology. Immunohistochemical staining for mucin genes products (MUC1, MUC2, MUC5AC, and MUC6), CK7, CK20, CA19.9, and CA125 were performed in tissue microarrays. Of note, we detected differences in the expression of MUC2 and CK20 between cases with and without PMP. Comparisons of borderline histology with that of benign/malignant tumors also revealed differences in MUC2 and CK20. Our results confirm that there is a distinct profile of intestinal ovarian tumors associated with pseudomyxoma, particularly with respect to the expression of the gel-forming mucin MUC2. The profile of borderline tumors, even in cases without PMP, was distinct from that of other primary mucinous tumors of the intestinal type, suggesting that borderline histology may represent a secondary tumor or a less aggressive variant of PMP. An appendiceal origin seems the most probable for this group of neoplasias.

A 10-year review of primary fallopian tube cancer at a community hospital: a high association of synchronous and metachronous cancers

Primary fallopian tube carcinomas (PFTC) are rare gynecological tumors infrequently diagnosed prior to operative intervention. A retrospective review was performed to characterize the distribution and clinicopathologic significance of these tumors. Identification of PFTC was achieved through a review of the tumor registry and medical record ICD-9 codes at a community teaching hospital. A total of 1.5% of all gynecological cancers were PFTC. Most patients were presumed to have ovarian cancer. Ultrasound had the highest sensitivity (82%) for preoperative diagnosis. Surgical exploration was needed for definitive diagnosis in all patients. Optimal debulking was predictive of survival and of a negative second-look laparotomy (P < 0.05). Twenty-five percent of patients had a metachronous cancer diagnosed prior to their fallopian tube cancer, and 22% had a synchronous gynecological malignancy diagnosed at the time of surgical exploration. The response rate to platinum-based chemotherapy was 78%. The 5-year survival rate was 87%, and the overall survival rate was 75%. The median follow-up was 38 months. This report details the diagnostic and therapeutic experience of patients with PFTC and describes the occurrence of synchronous and metachronous gynecological cancers.

Metastatic neoplasms involving the ovary: a review with an emphasis on morphological and immunohistochemical features

The ovary is a common site of metastatic tumour. In many cases of ovarian metastasis there is a known history of malignancy but in other cases the ovarian tumour is the first manifestation of disease. In this review metastatic colorectal, appendiceal, gastric, breast, pancreatic and biliary tract, hepatocellular, renal, transitional and cervical carcinomas and metastatic malignant melanoma involving the ovary are discussed, as is the issue of synchronous ovarian and endometrial carcinomas. Peritoneal tumours, including primary peritoneal carcinoma, mesothelioma and intra-abdominal desmoplastic small round cell tumour, involving the ovary are also discussed, together with a variety of other rare, metastatic ovarian neoplasms. Many metastatic adenocarcinomas involving the ovary, especially those exhibiting mucinous differentiation, closely mimic primary ovarian adenocarcinomas with morphologically bland areas simulating benign and borderline cystadenoma. This is referred to as a maturation phenomenon. In recent years immunohistochemistry, especially but not exclusively differential cytokeratin (CK7 and CK20) staining, has been widely used as an aid to distinguish between a primary and secondary ovarian adenocarcinoma. While immunohistochemistry undoubtedly has a valuable role to play and is paramount in diagnosis in some cases, the results must be interepreted with caution, especially in mucinous tumours, and within the relevant clinical context. We feel the significance of differential cytokeratin staining is not always understood by histopathologists and this can result in erroneous interpretation. We critically discuss the value of immunohistochemistry and associated pitfalls with each tumour type described.

Synchronous endometrioid carcinomas of the uterine corpus and ovary: alterations in the beta-catenin (CTNNB1) pathway are associated with independent primary tumors and favorable prognosis

Diagnosis of synchronous endometrioid carcinomas of the uterine corpus and ovary as either separate independent primary or as metastatic tumors requires careful consideration of a number of gross and histological features. Although such assessment is often sufficient, recent evidence has suggested that molecular analysis may facilitate the diagnosis in problematic cases. Furthermore, as independent synchronous tumors limited to the uterus and ovary are generally associated with favorable outcome, determination of genetic alterations associated with this group of neoplasms may indicate molecular markers of less aggressive behavior. We examined 12 cases of synchronous carcinomas of the uterus and ovary, correlating conventional gross and histological parameters with molecular genetic alterations common to single endometrioid carcinomas occurring in these sites. We identified a frequency of molecular alterations in both independent and metastatic tumors, including microsatellite instability (uterine tumors, 50% and 67%, respectively; ovarian tumors, 33% and 67%) and PTEN mutations (uterine tumors, 38% and 100%; ovarian tumors, 33% and 83%) that is higher than that observed in single sporadic tumors. Loss of heterozygosity for chromosome 17p and 10q was also frequently observed. Nuclear immunoreactivities for beta -catenin and CTNNB1 mutations were restricted to independent uterine and ovarian tumors and were absent in all of the metastatic tumors, providing direct evidence for a divergence of molecular oncogenetic mechanisms in the subset of synchronous endometrioid carcinomas. Furthermore, our data show that molecular genetic classification of synchronous independent versus metastatic tumors based on beta -catenin expression/mutation correlates with clinical outcome.

Ovarian carcinomas, including secondary tumors: diagnostically challenging areas

The differential diagnosis of ovarian carcinomas, including secondary tumors, remains a challenging task. Mucinous carcinomas of the ovary are rare and can be easily confused with metastatic mucinous carcinomas that may present clinically as a primary ovarian tumor. Most of these originate in the gastrointestinal tract and pancreas. International Federation of Gynecology and Obstetrics (FIGO) stage is the single most important prognostic factor, and stage I carcinomas have an excellent prognosis; FIGO stage is largely related to the histologic features of the ovarian tumors. Infiltrative stromal invasion proved to be biologically more aggressive than expansile invasion. Metastatic colon cancer is frequent and often simulates ovarian endometrioid adenocarcinoma. Although immunostains for cytokeratins 7 and 20 can be helpful in the differential diagnosis, they should always be interpreted in the light of all clinical information. Occasionally, endometrioid carcinomas may exhibit a microglandular pattern simulating sex cord-stromal tumors. However, typical endometrioid glands, squamous differentiation, or an adenofibroma component are each present in 75% of these tumors whereas immunostains for calretinin and alpha-inhibin are negative. Endometrioid carcinoma of the ovary is associated in 15-20% of the cases with carcinoma of the endometrium. Most of these tumors have a favorable outcome and they most likely represent independent primary carcinomas arising as a result of a Mullerian field effect. Although the criteria for distinguishing metastatic from independent primary carcinomas rely mainly upon conventional clinicopathologic findings, loss of heterozygosity and gene mutation analyses can be helpful. Transitional cell carcinomas are distinguished from undifferentiated carcinomas by the presence of thick, undulating papillae with smooth luminal borders, microspaces, and tumor cells with distinctive 'urothelial' appearance. Krukenberg tumors are metastatic adenocarcinomas traditionally perceived as composed of mucin-filled signet-ring cells associated with a striking proliferation of the ovarian stroma but many variations on this pattern occur.

Clinicopathologic analysis of the prognostic factors in women with coexistence of endometrioid adenocarcinoma in the endometrium and ovary

AIM

To compare the survival and prognostic factors of patients with dual primary ovarian and endometrial cancers (primary group), and endometrial cancers metastatic to the ovaries (metastatic group).

METHODS

Thirty-six patients with gross tumors confined to the pelvis and of endometrioid adenocarcinoma subtype in both the endometrium and ovary were selected from our file of 546 Japanese women with endometrial carcinoma. The patients were divided into two groups. Eleven were classified into the primary group. Twenty-five were classified into the metastatic group. Both univariate and multivariate regression analyses were carried out.

RESULTS

The mean age of the primary group was significantly younger than that of the metastatic group (45.2 years vs 51.2 years; P < 0.01). The cumulative 10-year survival of the primary group was significantly better than that of the metastatic group (90.9%vs 46.6%; P < 0.05). Univariate analyses showed that older age (P < 0.05) and the presence of lymphovascular space invasion (LVSI; P < 0.004) of the tumor of the uterus were significantly associated with a poor prognosis in the metastatic group. Multivariate analysis including the above variables showed no independent prognostic factor (older age, P < 0.60 and LVSI, P < 0.06).

CONCLUSION

When encountering women with coexisting endometrioid carcinoma in the endometrium and ovary with gross tumor limited to the pelvis, more attention should be paid to LVSI of the tumor of the uterus as a poor prognostic indicator.

[Independent endometrial and ovarian carcinomas: two cases of synchronous and metachronous endometrioid carcinomas]

Simultaneous carcinomas involving both the ovary and the endometrium may cause diagnostic difficulties, particularly if the tumors have a similar histology. We report two cases of independent endometrioid carcinomas of the endometrium and the ovary. Tumor development was synchronous in one case and metachronous in the other. These cases illustrate the morphological criteria helpful in distinguishing independent primaries from metastatic carcinomas which have a different therapeutic implication. Endometrial tumors were intra-mucosal without myometrial or vascular invasion, or tubal involvement and were associated with atypical complex hyperplasia (case 2). The ovarian tumors were uninodular, unilateral, without hilar invasion and were associated with endometriosis (case 2). The prognosis of endometrioid type carcinomas is better than for other histological types of carcinoma. Both our patients are well and disease free at 27 and 24 months.

Carcinosarcomas (malignant mullerian mixed tumors) of the uterus and ovary: a genetic study with special reference to histogenesis

The histogenesis of carcinosarcomas (malignant mullerian mixed tumors) of the female genital tract is still not completely understood. In the present study, several different molecular pathologic techniques were applied to determine the histogenesis of 15 uterine and ovarian carcinosarcomas. The patterns of X-chromosome inactivation and the presence of p53 and K-ras mutations were analyzed in the carcinomatous and sarcomatous components. Microsatellite analysis was also performed. Ten tumors were monoclonal, one was biclonal (collision tumor), and another was probably biclonal; the other three were of indeterminate histogenesis. These data indicate that most uterine and ovarian carcinosarcomas are monoclonal.