Tumor markers for ovarian cancer. A comparative immunohistochemical and immunocytochemical study of two commercial monoclonal antibodies (OV632 and OC125)

A comparative immunohistologic and immunocytologic study was performed to assess the immunoreactivity of the monoclonal antibodies OC125 and OV632, both directed at antigens present on epithelial ovarian tumors. OC125 reacted with 53 of 59 ovarian carcinomas, 20 of 20 uterine carcinomas, and 25 of 111 nongynecologic tumors (including 20 of 38 breast carcinomas). OV632 was demonstrated in 47 of 59 ovarian carcinomas, 11 of 20 uterine carcinomas, and only 7 of 111 nongynecologic tumors. With OV632 no reactivity was found in carcinomas of the breast or the gastrointestinal tract. Cytologic preparations of malignant effusions of patients with ovarian cancer showed reactivity with OC125 in 32 of 35 cases, and OV632 with positivity in 34 of 35 cases. Mesothelial cells in reactive effusions were OC125 positive in 16 of 20 cases but never showed positivity with OV632. The authors conclude that for histopathology a combination of OC125 and OV632 offers high sensitivity (0.86) and specificity (0.89) for ovarian cancer. For cytology, OV632 is the most specific tumor marker available.     

Monoclonal antibody SM047 as an immunohistochemical marker of ovarian adenocarcinoma

AIMS: This study describes the generation of a monoclonal antibody designated SM047 which binds to an epitope that is displayed by a multivalent antigen associated with the glycocalyx of ovarian adenocarcinoma cells. The study also investigates SM047 staining in adenocarcinomas of diverse sites in order to determine whether the antibody is specific for ovarian adenocarcinoma and of value in the confirmation of an ovarian origin when the site of primary tumour is unknown. METHODS AND RESULTS: SM047, an IgM monoclonal antibody, was the product of hybridoma cells derived from fusion of SP2 myeloma cells with splenocytes of a mouse that had been immunized with a membrane preparation of tumour (ovarian serous cystadenocarcinoma) and boosted with cells from a cell line established from a similar tumour in a different patient. Sixty-two primary ovarian adenocarcinomas (28 serous, 23 mucinous, five endometrioid and six clear cell), 69 adenocarcinomas arising primary at other sites and 10 mesotheliomas were stained with SM047. There was positive membrane staining, which was usually strong and widespread, in 27 of 28 ovarian serous carcinomas and in all ovarian endometrioid and clear cell carcinomas. Most ovarian mucinous tumours were negative or exhibited weak cytoplasmic staining. Staining was variable in the other tumours but there was positive staining of most endometrial, endocervical and pancreatic adenocarcinomas. Most colonic adenocarcinomas were negative or exhibited weak cytoplasmic staining. CONCLUSIONS: SM047 is strongly expressed in most ovarian serous adenocarcinomas and in other female genital tract adenocarcinomas, with the exception of ovarian mucinous tumours. The antibody may be useful in confirming the ovarian origin of an adenocarcinoma when used as part of a larger panel. This is especially so in the distinction between a non-mucinous ovarian adenocarcinoma, which usually exhibits strong membranous staining, and a colonic adenocarcinoma which is usually negative or exhibits weak cytoplasmic staining. These findings need to be confirmed by further study of larger numbers of cases.     

Changes in expression of differentiation markers between normal ovarian cells and derived tumors.

The marker profile of 18 samples of normal human ovarian tissues and 138 samples of their derived tumors was established using 51 monoclonal antibodies directed against intermediate filaments, ovarian carcinoma-specific antigens, general tumor-associated antigens and MHC-I/II antigens. Our data show that vimentin and keratins 7, 8, 18, and 19 were found in both epithelial and some nonepithelial ovarian tumors. Several tumor samples contained additional keratins 4, 10, 13, and 14, as well as desmin. BW 495/36 and to a lesser extent HMFG-2 were usually found in all ovarian tumors that contained simple epithelial keratins, except the absence of HMFG-2 in gonadal tumors as well as in dysgerminomas. In contrast to the keratin antibodies, these two panepithelial antibodies were negative in normal mesothelial cells and granulosa cells of the ovarian follicles. In general, the marker TAG-72 appeared useful for its discrimination between positively stained mucinous adenomas, the ovarian carcinomas as well as germ cell tumors, and the negatively stained gonadal tumors, serous adenomas, and cystomas. OV632 appeared useful in the distinction between negatively stained serous adenomas and positively stained serous carcinomas. In contrast, the monoclonal antibodies OC 125, OV-TL 3, OV-TL 16, and MOv 18 can be considered as pan-ovarian carcinoma markers, however without the discriminative capability as seen for OV632. These ovarian carcinoma-associated antigens were hardly found expressed in gonadal and germ cell tumors, except in the group of endodermal sinus tumors. HLA-I was found to be expressed in almost all nucleated cells, although loss of HLA-I expression was seen in areas of tumor cells. HLA-DR was negative in normal ovarian tissue, but heterogeneous expression was noticed in most of the epithelial tumors.     

In ovarian neoplasms, BRAF, but not KRAS, mutations are restricted to low-grade serous tumours

Genes of the RAF family, which mediate cellular responses to growth signals, encode kinases that are regulated by RAS and participate in the RAS/RAF/MEK/ERK/MAP-kinase pathway. Activating mutations in BRAF have recently been identified in melanomas, colorectal cancers, and thyroid and ovarian tumours. In the present study, an extensive characterization of BRAF and KRAS mutations has been performed in 264 epithelial and non-epithelial ovarian neoplasms. The epithelial tumours ranged from adenomas and borderline neoplasms to invasive carcinomas including serous, mucinous, clear cell, and endometrioid lesions. It is shown that BRAF mutations in ovarian tumours occur exclusively in low-grade serous neoplasms (33 of 91, 36%); these included serous borderline tumours (typical and micropapillary variants), an invasive micropapillary carcinoma and a psammocarcinoma. KRAS mutations were identified in 26 of 91 (29.5%) low-grade serous tumours, 7 of 49 (12%) high-grade serous carcinomas, 2 of 6 mucinous adenomas, 22 of 28 mucinous borderline tumours, and 10 of 18 mucinous carcinomas. Of note, two serous borderline tumours were found to harbour both BRAF and KRAS mutations. The finding that at least 60% of serous borderline tumours harbour mutations in two members of the ERK-MAP-kinase pathway (BRAF 36%, KRAS 30%) compared with 12% of high-grade serous carcinomas (BRAF 0%, KRAS 12%) indicates that the majority of serous borderline tumours do not progress to serous carcinomas. Furthermore, no BRAF mutations were detected in the other 173 ovarian tumours in this study.     

Immunocytochemistry of malignant mesothelioma: OV632 as a marker of malignant mesothelioma.

In pleural or ascitic effusions the cytomorphological distinction of adenocarcinoma cells, reactive mesothelial cells, and malignant mesothelioma cells often causes a diagnostic dilemma. The value of immunocytochemistry was investigated on cytological smears of 24 well-established cases of malignant mesothelioma, a selected series of 31 metastatic adenocarcinomas, and 20 smears of patients without known malignancy. In these smears we scored the immunoreactivity with a panel of four monoclonal antibodies. In addition to antibodies for epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA), the monoclonal antibody MOC31 and the ovarian carcinoma specific antibody OV632 were incorporated in the panel. With none of these four antibodies was immunostaining of reactive mesothelial cells found. CEA- and MOC31-positive tumour cells were frequent in metastatic adenocarcinomas, but occurred rarely in malignant mesotheliomas. EMA-positive tumour cells were found in all metastatic adenocarcinomas (100 per cent) and in most malignant mesotheliomas (83 per cent). In addition to the expected reactivity of OV632 with ovarian carcinomas, 22 of 24 malignant mesotheliomas contained immunopositive tumour cells, while only a small proportion of non-ovarian adenocarcinomas reacted with this antibody. This selective staining of malignant mesothelioma cells, but not reactive mesothelial cells, with OV632 now permits the positive identification of malignant mesothelioma cells in male patients.     

Use of immunohistochemical staining panel for characterisation of ovarian neoplasms.

Eighty five ovarian epithelial and non-epithelial tumours were studied by peroxidase histochemical staining for their reactivity with six monoclonal human milk fat globule (HMFG) antibodies, peanut agglutinin (PNA) lectin, and a monoclonal cytokeratin antibody. HMFG IIIC12 and cytokeratin antibodies distinguished epithelial from non-epithelial tumours. The staining patterns of mucinous and serous tumours were essentially different from each other; poorly differentiated anaplastic carcinomas showed similar antigenic content to that of the serous cystadenocarcinomas. Furthermore, staining with PNA lectin and HMFG antibodies was useful in distinguishing clear cell carcinomas from other malignant epithelial tumours of the ovary.     

Different proportions of aneusomic cells in ovarian inclusion cysts associated with serous borderline tumours and serous high-grade carcinomas support different pathogenetic pathways

Ovarian serous tumours may arise from the ovarian surface epithelium or from ovarian cortical epithelial inclusion cysts. However, little is known about the pathogenetic mechanisms involved in the progression from ovarian surface epithelium or inclusion cysts to neoplastic disease. In the present study, chromosomal aberrations typical of ovarian serous tumours were studied in ovarian surface epithelium and inclusion cysts. Ten ovaries with inclusion cysts obtained from patients without a gynaecological tumour, as well as 15 serous borderline tumours and 16 invasive high-grade serous carcinomas with inclusion cysts either in the ipsi- or in the contralateral ovary, were investigated by fluorescence in situ hybridization (FISH) using centromere enumeration probes directed against chromosomes 1, 6, 7, and X. The proportions of aneusomic cells were assessed. Trisomies 1 and 7 and monosomies 6 and X were present in the surface epithelium, inclusion cysts, and tumours, providing evidence for a link between the surface epithelium, and inclusion cysts, and serous neoplasia. Inclusion cysts generally harboured more aneusomic cells than the associated surface epithelium, suggesting an influence of the ovarian stroma on the development of chromosomal instability. Moreover, inclusion cysts associated with borderline tumours displayed a higher proportion of aneusomic cells than inclusion cysts associated with invasive high-grade carcinoma and than inclusion cysts in ovaries without neoplastic disease. These results suggest a genetic field defect of the inclusion cyst epithelium in serous borderline tumours. Invasive high-grade serous carcinomas, by contrast, may arise from single cell clones subject to a different set of genetic events.     

Immunohistochemical analysis of p53 protein and 72 kDa heat shock protein (HSP72) expression in ovarian carcinomas

Mutations of the tumour suppressor p53 gene have been reported in a variety of human malignant tumours, and are frequently associated with overexpression of p53 protein. To examine the significance of p53 gene alteration in malignant epithelial tumours of the ovary, we studied the immunohistochemical reactivity with a monoclonal antibody against p53 (PAb 1801) in 6 ovarian tumours of low malignant potential (LMP) and 32 ovarian carcinomas. The existence of any correlation of p53 overexpression with the clinicopathological features and with the immunohistochemical expression of 72 kDa heat shock protein (HSP72) and sex steroid receptors (oestrogen receptors; ER, progesterone receptors; PR) was also analysed. Expression of p53 was found in 2 of the 6 (33.3%) LMP tumours and in 15 of the 32 (46.9%) carcinomas. Strong expression of HSP72 was observed in 11 of the 17 (64.7%) p53-positive tumours, but only in 2 of the 21 (9.5%) p53-negative ones. Histologically, p53-positivity was observed in 7 of the 10 (70%) serous carcinomas, 4 of the 6 (66.7%) mucinous, 4 of the 10 (40%) endometrioid, and none of the 4 clear cell and 2 transitional cell carcinomas. Distribution of p53-positive cells in the tumour sections was homogenous in serous tumours, but heterogenous in mucinous lesions. All of the 4 carcinomas arising in endometriotic cysts were p53-negative. These differences support the thesis of heterogeneity in ovarian carcinogenesis. There was an inverse relationship between p53-positivity and sex steroid receptor status for ovarian carcinomas; 14 of the 15 p53-positive carcinomas were negative for both ER and PR, whereas 11 of the 17 p53-negative carcinomas were positive for ER and/or PR (P<0.01).     

Characterization of the specificity by immunohistology of a monoclonal antibody to a novel epithelial antigen of ovarian carcinomas

An immunohistological study, using the avidin-biotin-peroxidase complex method, was carried out to define the reactivity profile of a murine monoclonal antibody, MOv2, which recognizes a novel glycoprotidic antigen associated with ovarian epithelial tumors. Among the primary ovarian tumors tested, MOv2 immunostained 93% of mucinous and 75% of serous cystadenomas, 100% of mucinous, 81% of serous and 73% of endometrioid carcinomas. Undifferentiated and clear cell tumors revealed more limited reactivity with the antibody, whereas ovarian sex cord-stromal and germinal tumors were immunonegative. Positive reactions were also documented in omental metastases from primary ovarian carcinomas. No immunoreactivity was detected in normal ovarian epithelium, whereas the cells lining Walthard's nests adjacent to the fallopian tubes and a variety of normal epithelia were consistently immunolabeled. These included the lining epithelia of the gastrointestinal tract, bronchi and endocervix, and the epithelium of salivary, biliary and pancreatic ducts and sweat glands. To a lesser extent, positive reactions were detected in other surface epithelia, such as squamous and transitional epithelia. Among tumors other than ovarian, MOv2 consistently reacted with adenocarcinomas and squamous cell carcinomas from different sites, most notably breast, lung and gastrointestinal tract, and with transitional cell carcinomas. In contrast, no staining was demonstrated in non-epithelial malignancies. The antigen defined by MOv2 may be operationally useful as a marker of epithelial lineage in tumor histopathology. Its pattern of immunohistochemical distribution indicates that an antigenic phenotype shared by normal surface epithelia and non-ovarian carcinomas is strongly associated with common epithelial neoplasms of the ovaries.     

Wilms tumor gene product: sensitive and contextually specific marker of serous carcinomas of ovarian surface epithelial origin.

Carcinomas of ovarian surface epithelial origin can arise from, and often present at, extraovarian sites. There are few available markers for the positive identification of carcinomas of ovarian surface epithelial origin, which might aid in distinguishing them from metastatic carcinomas, such as of breast, colon, or lung origin. Recently, the Wilms tumor gene product (WT-1) has been shown to be expressed in ovarian surface and mesothelial epithelium. We tested the hypothesis that WT-1 would be a sensitive and specific marker of ovarian surface epithelium carcinomas. An archived series of 116 ovarian carcinomas (57 serous [43 ovarian, 14 extraovarian], 31 mucinous, 15 clear cell, 13 endometrioid), 118 breast carcinomas, 46 colonic carcinomas, and 45 nonsmall cell lung cancers were selected. A polyclonal antibody to the WT-1 gene product was applied to deparaffinized, formalin-fixed tissue sections after epitope retrieval. Fifty-two of 57 (93%) serous carcinomas of ovarian surface epithelial origin were WT-1-positive, in a nuclear pattern, with virtually all the tumor cell population positive in the majority of cases. None of the mucinous, clear cell, or endometrioid ovarian cancers were positive, and only 8 of 118 breast, 0 of 46 colonic, and 0 of 45 lung nonsmall cell carcinomas were WT-1-positive. These findings demonstrate that WT-1 is a highly sensitive and specific marker of serous carcinomas of ovarian surface epithelial origin (both ovarian and extraovarian). These results also contradict recent reports demonstrating WT-1 expression in both breast and lung carcinomas.     

In serous ovarian neoplasms the frequency of Ki-ras mutations correlates with their malignant potential

Ki-ras mutations by denaturing gradient gel electrophoresis (DGGE) and direct sequencing after microdissection. Point mutations at codon 12 were found in 7 of 20 tumours of low malignant potential (LMP) (35%) and in 2 of 6 well-differentiated carcinomas (33%). In contrast, no mutations were detected in the 11 poorly differentiated ovarian carcinoma samples or in the 7 serous cystadenomas. The frequency of Ki-ras mutations in serous ovarian tumours seems to correlate with the malignant potential of the neoplasms. The data favour the hypothesis of a de novo development of poorly differentiated ovarian carcinomas and do not support an evolution from LMP tumours or well-differentiated carcinomas. Received: 8 June 1998/Accepted: 8 October 1998     

My approach to and thoughts on the typing of ovarian carcinomas

Ovarian carcinomas of epithelial type comprise a heterogeneous group of neoplasms, each with a different underlying pathogenesis and natural behaviour. Accurate classification of ovarian carcinomas is important since each type may be associated with a different behaviour, natural history and outcome. Precise classification is also critical to determine whether alternative therapeutic strategies are appropriate for different tumour types. Previous studies have shown significant interobserver variation in the typing of ovarian carcinomas. There are several areas where there are particular difficulties; these include the distinction between high-grade serous and endometrioid adenocarcinomas and the distinction between a true clear cell carcinoma and clear cell areas within other adenocarcinomas. This review details my approach to the typing of ovarian carcinomas. Morphological assessment, which remains the mainstay in diagnosis, can be supplemented by immunohistochemistry which, for example, is useful in the distinction between serous carcinomas (WT1 positive) and other carcinomas (generally WT1 negative). In recent years, there has been emerging new information regarding the major underlying molecular events in several types of ovarian carcinoma. This has resulted in the acceptance that there are two distinct types of ovarian serous carcinoma. These are termed low-grade and high-grade serous carcinoma, but represent two distinct tumour types rather than low-grade and high-grade variants of the same neoplasm. The integration of clinical, morphological and molecular data has resulted in a more precise classification of ovarian carcinomas and has resulted in the proposal for a broad dualistic pathway of ovarian epithelial carcinogenesis with, in general, low-grade type 1 tumours evolving from benign and borderline neoplasms through a well-defined adenoma-carcinoma sequence, and high-grade type 2 neoplasms arising from an, as yet, undefined precursor lesion.     

Ovarian atypical endometriosis: its close association with malignant epithelial tumours

The incidence of ovarian atypical endometriosis and its association with malignant epithelial tumours in a consecutive series of cases during the period 1987 to 1995 were studied. Atypical glandular changes were observed in four (1.7%) of 255 ovarian endometriosis cases and one patient with ovarian atypical endometriosis developed subsequent endometrioid carcinoma in the abdominal wall. Fifty-four (24.1%) of the 224 ovarian cancers were associated with ovarian endometriosis; 21 with typical and 33 with atypical endometriosis. Clear cell carcinomas and endometrioid carcinomas were most frequently associated with endometriosis, with 54% (27 of 50 cases) and 41.9% (13 of 31), respectively. Atypical endometriosis was found in 18 clear cell carcinomas, in seven endometrioid carcinomas, in four serous carcinomas, in three mucinous borderline tumours, and in one serous borderline tumour. In 13 cases, the atypical endometriosis was in contiguity with malignant epithelial tumours. We consider that atypical endometriosis possesses a precancerous potential or is most frequently associated with clear cell and endometrioid carcinomas. Close screening of cellular atypia or hyperplasia in ovarian endometriosis and careful long-term follow-up of patients with atypical endometriosis is required.     

High-grade ovarian serous carcinoma exhibits significantly higher p16 expression than low-grade serous carcinoma and serous borderline tumour

AIMS: A dualistic pathway of ovarian serous carcinogenesis is now well established whereby high-grade serous carcinoma and low-grade serous carcinoma represent two distinct tumour types with a different underlying pathogenesis. The aim of this study was to compare expression of p16 INK4A (p16) in these two tumour types. We also included cases of serous borderline tumour, since these are considered to represent a precursor lesion of low-grade serous carcinoma. METHODS AND RESULTS: Cases of serous borderline tumour (n = 18), low-grade ovarian serous carcinoma (n = 22) and high-grade ovarian serous carcinoma (n = 24) were stained with a monoclonal antibody against p16. Cases were scored both with respect to intensity of immunoreactivity (weak, 1+; moderate, 2+; or strong, 3+) and distribution (0, negative or occasional positive cells; 1+, < 10% cells positive; 2+, 10-25% cells positive; 3+, 26-50% cells positive; 4+, 51-75% cells positive; or 5+, 76-100% cells positive). An immunohistochemical composite score was also calculated (0-15) by multiplying the intensity and distribution scores. There was a statistically significant difference in p16 immunoreactivity with respect to intensity, distribution and composite score between high-grade serous carcinoma and each of the other two groups, with the high-grade neoplasms exhibiting stronger and more diffuse positivity. Most high-grade serous carcinomas exhibited positivity of close to 100% of tumour cells. There was no significant difference in p16 expression between the borderline tumours and low-grade serous carcinomas. CONCLUSIONS: The increased expression of p16 in high-grade serous carcinoma compared with low-grade serous carcinoma and serous borderline tumour is in keeping with a different underlying pathogenesis. p16 may be implicated in the development of high-grade serous neoplasia within the ovary and elsewhere within the female genital tract.     

Uncommon ovarian epithelial tumours

Epithelial ovarian tumours represent the most common type of ovarian tumour. Most of malignant cases represent high-grade serous, clear cell and endometrioid carcinomas; borderline serous and mucinous tumours of intestinal type are less common. This review focuses on the uncommon or rare epithelial tumours of the ovary which include borderline and malignant Brenner tumours, the recently-described mesonephric-like carcinoma of the ovary, and primary ovarian neuroendocrine tumours, with emphasis on helpful and diagnostic features.     

Hyaline globules in ovarian tumours

Hyaline eosinophilic globules have so far been described in a restricted variety of tumour types. We have noted their presence in a variety of gynaecological malignancies, in particular mixed Müllerian tumours and other epithelial ovarian tumours. We therefore studied their incidence and distribution in a series of malignant, borderline and benign epithelial ovarian tumours, and endometrial and endocervical adenocarcinomas. Hyaline eosinophilic globules were found in all 30 mixed Müllerian tumours from various sites in the female genital tract, 22 of 30 clear cell carcinomas, seven of 30 serous, two of 30 mucinous, and one of 30 endometrioid carcinomas examined, and were also seen in metastases from these tumours. They were present in only two of 25 borderline serous, one of 25 borderline mucinous tumours, and in four of 50 benign serous and one of 50 benign mucinous tumours. The globules were not found in any of 25 Brenner tumours examined, nor in 30 endometrial or 30 endocervical adenocarcinomas. The globules were periodic acid–Schiff positive after diastase, stained positively with PTAH, and were immunoreactive for α-1-antitrypsin. This study therefore demonstrates that eosinophilic globules are not specific for any particular tumour. However, their frequency in malignant mixed Müllerian tumours suggests that this diagnosis should be carefully excluded whenever these globules are present in epithelial tumours of the female genital tract.     

Metallothionein expression and nuclear size in benign,borderline, and malignant serous ovarian tumours

Metallothioneins (MTs) are low-molecular-weight proteins involved in metalloregulatory functions such as cell proliferation, growth, and differentiation. In recent years, MT expression has been linked with carcinogenesis, resistance to cancer therapy, and tumour progression. However, the significance of MT expression in ovarian cancers is at present inadequately documented. In this study, MT immunohistochemistry was performed in 12 benign, 14 borderline, and eight malignant serous tumours of the ovary. The intensity of the immunostaining was evaluated by image analysis. There was a significantly higher number of MT-immunopositive cells in the multilayered epithelial cells of borderline serous tumours (atypical proliferative serous tumours) than in the single layered epithelial cells within the same tumour, and in the single cell layer of benign serous tumours. There was no difference in the expression of MTs in the single layered tumour cells of benign and borderline serous tumours. Significantly higher numbers of MT-immunopositive cells were observed in both the single and the multilayered epithelial cells of serous carcinomas, the highest number being observed in the multiple layers of serous carcinomas. The positively stained malignant tumour cells in both single and multiple layers were larger than the negatively stained cells in benign, borderline, and malignant serous ovarian tumours. There was moderate to intense staining. These findings indicate that there is increased expression of MTs in the progression of malignancy, which could be used as a marker in grading the three groups of ovarian serous tumours and for determining prognosis. Copyright © 1999 John Wiley & Sons, Ltd.     

Evolution of the concept and termiology of borderline ovarian tumours

The borderline category of ovarian tumours was established in the early 1970s because of the observation that a group of proliferative epithelial ovarian tumours lacking invasion that generally behaved in a benign fashion occasionally pursued an indolent malignant course. Over the last 25 years, a large database on these tumours has been accrued. Recent studies suggest that the borderline group can now be subclassified into benign and malignant neoplasms. The survival for patients with serous borderline tumours confined to the ovaries is virtually 100%. Patients with ovarian serous borderline tumours with invasive peritoneal implants have a 34% mortality rate; therefore, these cases are classified as low grade carcinomas. Micropapillary serous carcinoma, a distinctive neoplasm that fails to display unequivocal evidence of invasion and therefore has been included in the borderline category, is strongly associated with invasive implants and recurs as invasive carcinoma. After these neoplasms with invasive implants are excluded from the group of tumours classified as borderline, the remaining advanced stage serous borderline tumours (those with non-invasive implants) have a disease-specific survival rate of nearly 100% and should be considered benign. In a similar fashion, the vast majority of mucinous borderline tumours reported to display aggressive behaviour have been associated with the clinical syndrome of pseudomyxoma peritonei. It is now clear that pseudomyxoma peritonei is a condition of appendiceal origin in virtually all cases. In addition, there is a small group of mucinous carcinomas typically from the pancreas and biliary system that present with relatively bland-appearing metastases to the ovaries that closely simulate mucinous borderline tumours. Once these metastatic carcinomas and mucinous tumours associated with pseudomyxoma peritonei are removed from the borderline category, the remaining mucinous borderline tumours are always confined to the ovaries and have a benign behaviour. Finally, review of the literature indicates the other epithelial types of borderline tumours (endometrioid, clear cell and transitional cell) behave in a benign fashion. Since borderline tumours can now be classified into benign and malignant types, the borderline category has no further utility and can be abandoned. This will be of great benefit to patients and clinicians, and will also help in more clearly focusing research efforts on ovarian cancer.     

Low-grade serous carcinomas of the ovary contain very few point mutations

It has been well established that ovarian low-grade and high-grade serous carcinomas are fundamentally different types of tumours. While the molecular genetic features of ovarian high-grade serous carcinomas are now well known, the pathogenesis of low-grade serous carcinomas, apart from the recognition of frequent somatic mutations involving KRAS and BRAF, is largely unknown. In order to comprehensively analyse somatic mutations in low-grade serous carcinomas, we applied exome sequencing to the DNA of eight samples of affinity-purified, low-grade, serous carcinomas. A remarkably small number of mutations were identified in seven of these tumours: a total of 70 somatic mutations in 64 genes. The eighth case displayed mixed serous and endometrioid features and a mutator phenotype with 783 somatic mutations, including a nonsense mutation in the mismatch repair gene, MSH2. We validated representative mutations in an additional nine low-grade serous carcinomas and 10 serous borderline tumours, the precursors of ovarian low-grade, serous carcinomas. Overall, the genes showing the most frequent mutations were BRAF and KRAS, occurring in 10 (38%) and 5 (19%) of 27 low-grade tumours, respectively. Except for a single case with a PIK3CA mutation, other mutations identified in the discovery set were not detected in the validation set of specimens. Our mutational analysis demonstrates that point mutations are much less common in low-grade serous tumours of the ovary than in other adult tumours, a finding with interesting scientific and clinical implications.     

Immunohistochemistry of ovarian granulosa cell tumours

Summary Paraffin-embedded material of 47 ovarian tumours primarily diagnosed as granulosa cell tumours, including 2 cases of juvenile granulosa cell tumour, were studied immunohistochemically for the presence of intermediate filament proteins, epithelial membrane antigen and tumour markers. Forty-one lesions, including the 2 juvenile granulosa cell tumours, were vimentin positive, while keratin and epithelial membrane antigen expression could not be detected. Six tumours primarily diagnosed as poorly differentiated malignant granulosa cell tumours were vimentin negative, showed a mild to moderate positivity for keratin and intense positivity with the anti-epithelial membrane antigen antibody. These latter tumours were therefore classified as undifferentiated ovarian carcinomas, corresponding to their significantly poorer prognosis and shorter survival when compared with the granulosa cell tumours. Two of these six tumours were positive for carcino-embryonic antigen. Two small cell carcinomas of the ovary studied in addition expressed keratin in a proportion of tumour cells while no epithelial membrane antigen or vimentin was detectable. None of the tumours tested for alpha-fetoprotein, human chorionic gonadotrophin, human placental alkaline phosphatase and human placental lactogen, were positive.The data indicate the value of antibodies directed against intermediate filament proteins and epithelial membrane antigen to distinguish granulosa cell tumours from poorly differentiated carcinomas, a worthwhile distinction considering the much better prognosis of granulosa cell tumours.