Borderline ovarian tumors

Borderline ovarian tumors account for approximately 15% of all epithelial ovarian tumors. In the early 1970s, borderline tumors were categorized as either serous or mucinous with overall survival rates of 75–90%. Since then, it has been recognized that the two categories are heterogonous. There are now many different groups following the recognition of serous tumors with microinvasion, non‐invasive and invasive peritoneal implants and a micropapillary pattern, and of mucinous tumors with microinvasion, intraepithelial carcinoma and pseudomyxoma peritoneal implants, in addition to further delineation of endometrial, clear cell and transitional cell tumors with atypical proliferation. This review outlines the most recent information regarding the epidemiology, pathology and clinical management of borderline tumors. Surgical management to excise all visible tumors remains the cornerstone of therapy. Because borderline ovarian tumors often occur in reproductive‐age women, fertility is an important issue. Conservative surgery is a safe in carefully selected patients. Effective non‐surgical therapies are yet to be identified.     

Borderline ovarian tumour: pathological diagnostic dilemma and risk factors for invasive or lethal recurrence

By comparison with ovarian carcinomas, borderline ovarian tumours are characterised clinically by superior overall survival, even in women with peritoneal spread. In this Review, we aimed to clarify the histological and clinical factors potentially defining a high-risk group in whom disease is likely to evolve to invasive disease. Invasive peritoneal implants (in serous borderline ovarian tumours) and residual disease after surgery were the two factors clearly identified. Other factors are controversial owing to increased risk of invasive recurrence: micropapillary patterns in serous borderline ovarian tumour, intraepithelial carcinoma in mucinous lesions, stromal microinvasion in serous lesions, and use of cystectomy in mucinous borderline ovarian tumours. The pathologist has a pivotal role in assessment of the borderline nature of ovarian tumours and in identification of high-risk criteria, most of which are histological. But, reproducibility of the histological interpretation of some of these potential criteria--eg, classification of peritoneal implants (particularly in desmoplastic subtype), stromal microinvasion, micropapillary patterns, and intraepithelial carcinoma in mucinous borderline ovarian tumours--remains unclear, and should be investigated.     

Immunohistochemical staining of GLUT1 in benign, borderline, and malignant ovarian epithelia

BACKGROUND: Aberrant expression of the facilitative glucose transporter GLUT1 is found in a wide spectrum of epithelial malignancies. The authors describe an immunohistochemical study of GLUT1 expression in benign, borderline, and malignant ovarian epithelia. METHODS: One hundred forty one formalin-fixed, paraffin-embedded sections were immunostained with rabbit anti-GLUT1 using the streptavidin-biotin method. The samples were as follows: 3 endometriotic cysts, 9 serous cystadenomas, 15 mucinous cystadenomas, 17 noninvasive borderline implants, 3 invasive borderline implants, and 3 endosalpingiosis. In addition, 35 borderline tumors (26 serous, 7 mucinous, 2 seromucinous) and 56 adenocarcinomas (50 serous, 4 endometrioid, 2 mucinous) were stained. RESULTS: Benign serous and mucinous cystadenomas and endosalpingiosis were non-staining with GLUT1 antiserum. Twenty-eight of 35 borderline tumors (80%) stained positively, with weak to moderate (1-2+ out of 3) staining intensity and focal or patchy distribution. Seventeen noninvasive serous borderline implants were negatively stained; however, three invasive serous borderline implants were positively stained with GLUT1 antiserum. Fifty four of 56 ovarian carcinomas (96%) stained positively, with moderate to strong (2-3+ out of 3) intensity and multifocal distribution. CONCLUSIONS: GLUT1 is a consistent marker of ovarian epithelial malignancy. GLUT1 staining is absent in benign ovarian epithelial tumors, and shows progressively more staining in invasive tumors as compared to borderline tumors. Anti-GLUT1 antibody may be useful in distinguishing invasive from noninvasive serous borderline implants.     

Quantitative analysis of follicle-stimulating hormone receptor in ovarian epithelial tumors: a novel approach to explain the field effect of ovarian cancer development in secondary mullerian systems

The role of FSHR expression in ovarian cancer development is not clear. We examined quantitative expression of FSHR in different types of OET, presumed precursor lesions and peritoneal implants and further discussed FSH as a key growth-promotion factor for the process of ovarian epithelial tumorigenesis. Thirty-five primary OET specimens, including 5 serous cystadenomas, 4 papillary serous cystadenomas, 9 SBTs and 17 serous carcinomas, were examined for quantitative FSHR expression. Ten paired samples (3 benign cystadenomas, 5 SBTs and 2 carcinomas) were obtained from several morphologically different areas, including benign-looking, borderline and cancerous areas in the same OETs, and from the remaining ovarian tissue and contralateral ovaries. Competitive RT-PCR was performed to measure the quantitative expression of FSHR in each tissue sample. FSHR expression levels were compared among nonpaired samples and within paired samples. We found that OSE had the lowest FSHR expression, whereas antral follicles had the highest level. Within benign OETs, papillary serous cystadenomas have 4.9-fold higher FSHR levels than nonpapillary serous cystadenomas. SBTs had the highest level of FSHR expression, which was 12.8-fold, 2.7-fold and 2.4-fold higher than that of serous cystadenomas, papillary serous cystadenomas and grade 1 carcinomas, respectively. A similarly high level of FSHR mRNA was found in peritoneal implants, which were associated with SBTs. FSHR levels among serous carcinomas decreased with an increase in carcinoma grade. Grade 3 carcinomas had the lowest FSHR level, which was similar to that of serous cystadenomas, while grade 1 carcinomas had 6.5-fold higher FSHR levels than those in serous cystadenomas. Our results suggest that not only serum FSH but also FSHR in ovarian epithelium may play important roles in ovarian OET development. Both the receptor and ligand may act in a synergistic way to promote tumor growth. The observation that high FSHR levels are present in peritoneal implants suggests that FSH may also play a similar role in the development of peritoneal serous tumors. From this perspective, circulating FSH may be considered a driving force in the field effect theory for the development of both ovarian neoplasms and their associated peritoneal implants. However, the exact role of FSH and/or FSHR in the development of epithelial tumors arising in both the ovary and peritoneum needs further investigation.     

Serous borderline tumors of the ovary. A clinicopathologic, immunohistochemical, and quantitative study of 44 cases.

The clinicopathologic features of 44 serous borderline tumors (SBT) of the ovary were evaluated. Nineteen were Stages II and III, and 9 had invasive peritoneal implants. All 19 patients received chemotherapy and 4, who had invasive implants, died of disease after 3, 4.3, 8, and 9 years. The other 25 patients were free of tumor 1-14 years (mean, 5.3 years) after surgery. Coexpression of low molecular weight keratins (AE1, CAM 5.2) and vimentin was found in all tumors and their implants. No significant differences were found between SBT with different volume-corrected mitotic indices (M/Vi) with respect to gross features, presence or absence of implants, stage, and survival. Cytometric DNA analysis also was performed on the primary ovarian tumors and the implants. Twenty-one primary tumors had diploid or tetraploid histograms, and 23 had aneuploid histograms. DNA ploidy of the primary ovarian tumors did not correlate with gross features, the presence or absence of implants, M/Vi, stage, and survival. The data from this study confirm that most SBT are clinically benign, but SBT with invasive implants may behave aggressively. Expression of intermediate filaments, M/Vi, and DNA ploidy evaluation of the primary ovarian tumors seem to be of no value in predicting prognosis. However, four of seven patients with aneuploid DNA implants died of tumor.     

Outcomes after conservative treatment of advanced-stage serous borderline tumors of the ovary

BackgroundThe aim of this study was to assess the outcomes of the largest series of patients treated conservatively for a stage II or III serous borderline ovarian tumor.Materials and methodsFrom 1969 to 2006, 41 patients were treated conservatively for an advanced-stage serous borderline ovarian tumor. Patient outcomes were reviewed.ResultsTwenty patients had undergone a unilateral salpingo-oophorectomy, 18 a unilateral cystectomy and two bilateral cystectomy (unknown for one patient). Three patients had invasive implants. The median duration of follow-up was 57 months (range 4–235). The recurrence rate was high (56%), but overall survival remained excellent (100% at 5 years, 92% at 10 years). One death had occurred due to an invasive ovarian recurrence. Eighteen pregnancies (nine spontaneous) were observed in 14 patients.ConclusionsThis study demonstrates that spontaneous pregnancies can be achieved after conservative treatment of advanced-stage borderline ovarian tumors (with noninvasive implants) but the recurrence rate is high. Nevertheless, this high rate has no impact on survival. Conservative surgery can be proposed to patients with a borderline tumor of the ovary and noninvasive peritoneal implants. Should infertility persist following treatment of the borderline tumor, an in vitro fertilization procedure can be cautiously proposed.     

Research developments on the histopathology and prognostic predictors of serous borderline tumor of ovary

Serous borderline tumor of ovary （SBT） includes two subtypes of typical serous borderline tumor and micropapillary variant, which have different histopathology features. Although SBTs behave in either way of the benign counterparts or malignant serous carcinomas, microinvasion, peritoneal implants, and nodal involvement are all very common in both subtypes of typical SBT and the micropapillary variant. The prognosis of the patients with serous borderline tumor of ovary and the mechanism of the microinvasion, peritoneal implantation and nodal involvement are still being debated, nor is there universal agreement about the management of SBT. To identify the histopathologic features, prognostic predictors of the SBT, and its association with ovarian serous carcinomas, we reviewed the majority of the relevant papers published in recent literature.     

Research Developments on the Histopathology and Prognostic Predictors of Serous Borderline Tumor of Ovary

Serous borderline tumor of ovary (SBT) includes two subtypes of typical serous borderline tumor and micropapillary variant, which have different histopathology features. Although SBTs behave in either way of the benign counterparts or malignant serous carcinomas, microinvasion,peritoneal implants, and nodal involvement are all very common in both subtypes of typical SBT and the micropapillary variant.The prognosis of the patients with serous borderline tumor of ovary and the mechanism of the microinvasion, peritoneal implantation and nodal involvement are still being debated, nor is there universal agreement about the management of SBT. To identify the histopathologic features, prognostic predictors of the SBT, and its association with ovarian serous carcinomas, we reviewed the majority of the relevant papers published in recent literature.     

Invasive and noninvasive implants in ovarian serous tumors of low malignant potential

Ovarian serous tumors of low malignant potential ("borderline" serous tumors) are classified according to the histologic features of the primary ovarian tumor, without regard to any coexisting extraovarian disease. The peritoneal implants display a range of histologic appearances, ranging from benign glands (endosalpingiosis), to noninvasive papillary glandular proliferations resembling the ovarian neoplasms, to irregular glands associated with a desmoplastic stroma and having features of invasive disease. This review of 16 patients with histologically documented extraovarian tumor implants seen at Indiana University Medical Center, Indianapolis, and 13 patients whose tumor implants have been previously described in the literature indicates that the clinical stage of disease has much greater prognostic significance than does the implant histologic features. There is a tendency for patients with more advanced disease to have invasive implants. However, within a given clinical stage, disease progression or recurrence was not influenced by the presence or absence of invasive histologic characteristics in the tumor implants.     

Serous ovarian tumors of low malignant potential with peritoneal implants

Between 1956 and 1985, 82 patients with metastatic low-grade serous ovarian carcinoma, subsequently reclassified by pathologic review as serous ovarian tumors of low malignant potential with peritoneal implants, were seen at the authors' institution. Median age was 34 years (range, 17-64 years). Original stage distribution was as follows: 32 Stage II, 46 Stage III, and four Stage IV. Peritoneal implants in 72 patients were classified as benign (22 patients), noninvasive (37), or invasive (13). For ten patients, implants were clinically documented but histologic material was unavailable. The most common sites of peritoneal implants included the pelvic peritoneum (42), omentum (33), uterus (33), and fallopian tube (26). All patients underwent primary surgery. Postoperative therapy consisted of radiotherapy in 18 patients, single-agent chemotherapy in 37 patients, combination chemotherapy in 25 patients, and no therapy in two patients. Second-look laparotomy documented response to chemotherapy in 42% of patients with no gross residual disease and in 80% of patients with macroscopic residual disease (40% complete response, 40% partial response). Disease-free survival rates were 95% at 5 years and 91% at 10 years. The International Federation of Gynecologists and Obstetricians (FIGO) stage, extent of residual disease, type of postoperative treatment, and type of peritoneal implants had no effect on survival. Based on a comparison of the present study's findings with those in the literature, the authors propose possible explanations for differences in survival by type of peritoneal implants and outline recommendations for clinical management until further studies elucidate the role of postoperative therapy.     

Apolipoprotein E is required for cell proliferation and survival in ovarian cancer

Apolipoprotein E (ApoE) has been recently identified as a potential tumor-associated marker in ovarian cancer by serial analysis of gene expression. ApoE has long been known to play a key role in lipid transport, and its specific isoforms may participate in atherosclerogenesis. However, its role in human cancer is not known. In this study, apoE expression was frequently detected in ovarian serous carcinomas, the most common and lethal type of ovarian cancer. It was not detected in serous borderline tumors and normal ovarian surface epithelium. Inhibition of apoE expression using an apoE-specific siRNA led to G(2) cell cycle arrest and apoptosis in an apoE-expressing ovarian cancer cell line, OVCAR3, but not in apoE-negative cell lines. Furthermore, the phenotype of apoE siRNA-treated OVCAR3 cells was reversed by expressing engineered mutant apoE with introduced silent mutations in the siRNA target sequence. Expression of apoE in nuclei was significantly associated with a better survival in patients who presented peritoneal effusion at the time of diagnosis (5-year follow-up, P = 0.004). This study suggests a new role of apoE in cancer as apoE expression is important for the proliferation and survival in apoE-expressing ovarian cancer cells.     

Expression of the MAGE-A4 and NY-ESO-1 cancer-testis antigens in serous ovarian neoplasms.

PURPOSE: The cancer-testis (CT) family of antigens is expressed in a variety of malignant neoplasms and is silent in normal tissues, except for the testis. Expression of two members of this family, MAGE-A4 and NY-ESO-1, has been described in melanomas, germ cell tumors, certain carcinomas and sarcomas, and more recently in uterine neoplasms. The objective of this study was to evaluate the extent and prognostic significance of CT antigen expression in ovarian serous neoplasms. EXPERIMENTAL DESIGN: Seventy-four patients with ovarian neoplasms, including 10 with serous cystadenomas, 11 with serous tumors of borderline malignancy, and 53 with serous carcinomas, were studied. Immunohistochemistry was performed with the 57B monoclonal antibody, which recognizes predominantly the MAGE-A4 antigen and the D8.38 antibody that recognizes NY-ESO-1. RESULTS: MAGE-A4 expression was found to be present in 57% of the serous carcinomas and only in 9% of the serous tumors of borderline malignancy. No staining was detected in serous cystadenomas or in the normal ovary. In 8 of 30 positively stained serous carcinomas, >50% of the tumor cells expressed MAGE-A4. NY-ESO-1 expression was seen in 19% of the serous carcinomas, whereas serous tumors of borderline malignancy and cystadenomas were negative. A significant inverse correlation was found between MAGE-A4 expression and patient survival (P = 0.016). Multivariate analysis revealed that both tumor stage and MAGE-A4 expression were independent predictors of patient survival (P = 0.022 and P = 0.013, respectively). CONCLUSIONS: Cancer-testis antigen expression in ovarian serous neoplasms correlates directly with their degree of malignancy. MAGE-A4 expression, and to a lesser degree NY-ESO-1 expression, is characteristic of the majority of serous carcinomas. Determining the degree of MAGE-A4 expression in these tumors may provide important prognostic information. Finally, MAGE-A4 may represent a novel target for immunotherapy in serous ovarian neoplasms.     

Molecular Characterization of 103 Ovarian Serous and Mucinous Tumors

The pathogenesis of ovarian carcinomas is heterogeneous, with even the same entities showing great variance. In our study we investigated the mutations of the BRAF, KRAS, and p53 genes in serous and mucinous borderline tumors and in low grade and high grade serous and mucinous tumors. The mutations of BRAF and KRAS genes have been shown in 60% of borderline and low grade (well differentiated) serous and mucinous tumors, but very rarely in high grade (moderately and poorly differentiated) carcinomas. However mutations of p53 are very common in high grade tumors and this indicates a "dualistic" model of ovarian tumorigenesis. A total of 80 serous tumors, including serous borderline, low grade and high grade tumors, and 23 mucinous tumors, including borderline and invasive tumors were analysed for BRAF and KRAS mutations using real time PCR method followed by melting point analysis. P53 mutation was investigated by immunohistochemistry. We assumed mutation of the p53 gene when 100% of tumor cells showed strong nuclear positivity. We observed differences in genetic alterations in the development of the low grade tumors and between low and high grade tumors too. In some bilateral or stage II-III cases we observed differences between the mutation status of the left and right ovarian tumors and between the primary tumor and its implants. In one case in a tumor with micropapillary pattern showing high grade nuclear atypia we could detect mutations in both KRAS and p53 genes. The majority of our mucinous ovarian tumor cases showed a KRAS mutation. We have not found mutations of the BRAF and p53 genes in these cases. We have found as have others, that there is a dualistic pathway of ovarian carcinogenesis. In the majority of cases, low grade epithelial tumors develop in a stepwise manner due to genetic alterations of the members of MAP-kinase pathway; however mutation of the p53 gene is the key event in the development of high grade tumors.     

Mutations in BRAF and KRAS characterize the development of low-grade ovarian serous carcinoma

Activating mutations in KRAS and in one of its downstream mediators, BRAF, have been identified in a variety of human cancers. To determine the role of mutations in BRAF and KRAS in ovarian carcinoma, we analyzed both genes for three common mutations (at codon 599 of BRAF and codons 12 and 13 of KRAS). Mutations in either codon 599 of BRAF or codons 12 and 13 of KRAS occurred in 15 of 22 (68%) invasive micropapillary serous carcinomas (MPSCs; low-grade tumors) and in 31 of 51 (61%) serous borderline tumors (precursor lesions to invasive MPSCs). None of the tumors contained a mutation in both BRAF and KRAS. In contrast, none of the 72 conventional aggressive high-grade serous carcinomas analyzed contained the BRAF codon 599 mutation or either of the two KRAS mutations. The apparent restriction of these BRAF and KRAS mutations to low-grade serous ovarian carcinoma and its precursors suggests that low-grade and high-grade ovarian serous carcinomas develop through independent pathways.     

Characterization of active mitogen-activated protein kinase in ovarian serous carcinomas.

PURPOSE: Mitogen-activated protein kinase (MAPK) plays a pivotal role in signal transduction. Activation of MAPK is regulated by upstream kinases including KRAS and BRAF, which are frequently mutated in low-grade ovarian serous carcinoma. This study evaluates the expression of active MAPK in ovarian serous carcinomas, with response to treatment and survival. EXPERIMENTAL DESIGN: Expression of active MAPK was assessed by immunohistochemistry in 207 cases of ovarian serous tumors. Immunoreactivity was correlated with tumor grade, mutational status of KRAS and BRAF, in vitro drug resistance, and clinical outcome. RESULT: There was a lower frequency of expression of active MAPK in high-grade ovarian serous carcinomas as compared with low-grade serous tumors, including borderline tumors and low-grade serous carcinoma (P < 0.001). Active MAPK was present in all of the 19 low-grade tumors with either KRAS or BRAF mutations as well as in 14 (41%) of 34 tumors with wild-type KRAS and BRAF in both low- and high-grade carcinomas. Expression of active MAPK alone served as a good survival indicator in the 2-year follow-up (P = 0.037) but not in the 5-year follow-up (P = 0.145). However, a combination of expression of active MAPK and in vitro sensitivity of paclitaxel significantly correlated with a better prognosis in 5-year survival rate (P = 0.048) in patients with advanced-stage high-grade serous carcinoma. CONCLUSIONS: Active MAPK is more frequently expressed in low-grade than in high-grade ovarian serous carcinoma. Active MAPK serves as a good prognostic marker in patients with high-grade serous carcinomas.     

GLUT-1和DNA-PKcs在卵巢浆液性肿瘤组织中的表达及其意义

背景与目的:已知肿瘤细胞生长所需能量是通过葡萄糖转运体蛋白1(glucose transporter protein 1,GLUT-1)完成的葡萄糖代谢来提供的.另外,参与基因损伤修复的催化亚单位--DNA蛋白激酶(DNA-dependent protein kinase catalytic subunit,DNA-PKcs)在肿瘤形成中也起着非常重要的作用.本研究旨在探讨GLUT-1和DNA-PKcs在卵巢浆液性肿瘤组织中的表达及其与肿瘤生物学行为的关系和意义.方法:免疫组化方法检测80例卵巢浆液性肿瘤组织中GLUT-1、DNA-PKcs的表达,分析其异常表达与临床病理参数之间的相关性.以正常卵巢组织20例为对照.结果:正常卵巢组织GLUT-1表达全阴性,DNA-PKcs表达全阳性.GLUT-1在良性、交界性、恶性卵巢浆液性肿瘤中的表达呈增高的趋势,与卵巢浆液性肿瘤的发生发展呈正相关(rs=0.943,P＜0.01);在恶性肿瘤中的阳性率(100%)明显高于交界性(55%).DNA-PKcs在良性、交界性和恶性卵巢浆液性肿瘤中的阳性率分别为95%、90%、60%,差异有统计学意义(P＜0.01).GLUT-1与DNA-PKcs的表达呈负相关(rs=-0.270,P＜0.01).GLUT-1表达与临床分期、腹腔种植、腹水、淋巴结转移均相关(P＜0.05);DNA-PKcs仅与临床分期和淋巴结转移相关(P＜0.05),与腹水、腹腔种植无关(P＞0.05).结论:GLUT-1的异常表达和DNA-PKcs的丢失与卵巢浆液性肿瘤恶变相关.     

Diagnosis,Treatment, and Follow‐Up of Borderline Ovarian Tumors

Borderline ovarian tumors represent a heterogeneous group of noninvasive tumors of uncertain malignant potential with characteristic histology. They occur in younger women, are present at an early stage, and have a favorable prognosis, but symptomatic recurrence and death may be found as long as 20 years after therapy in some patients. The molecular changes in borderline ovarian tumors indicate linkage of this disease to type I ovarian tumors (low-grade ovarian carcinomas). The pathological stage of disease and subclassification of extraovarian disease into invasive and noninvasive implants, together with the presence of postoperative macroscopic residual disease, appear to be the major predictor of recurrence and survival. However, it should be emphasized that the most important negative prognostic factor for recurrence is just the use of conservative surgery, but without any impact on patient survival because most recurrent diseases are of the borderline type—easily curable and with an excellent prognosis. Borderline tumors are difficult masses to correctly preoperatively diagnose using imaging methods because their macroscopic features may overlap with invasive and benign ovarian tumors. Over the past several decades, surgical therapy has shifted from a radical approach to more conservative treatment; however, oncologic safety must always be balanced. Follow-up is essential using routine ultrasound imaging, with special attention paid to the remaining ovary in conservatively treated patients. Current literature on this topic leads to a number of controversies that will be discussed thoroughly in this article, with the aim to provide recommendations for the clinical management of these patients.     

Borderline epithelial tumours of the ovary--a retrospective analysis of 31 cases

Thirty one cases of epithelial borderline tumours of the ovary recorded over a period of six years were reviewed. The incidence of borderline tumours was 6% in relation to ovarian epithelial malignancies, with serous and mucinous types comprising three fourth of the lesions. The serous tumours were bilateral in 39%, revealed surface growth in 17% and had peritoneal implants in 11% of cases. The mucinous tumours were bilateral in 11% and had associated pseudomyxoma peritonei in 22% of cases. Nuclear grade appeared to correlate with extraovarian spread and surface growth in the serous borderline tumours, but not in the mucinous borderline tumours. The endometrioid borderline tumours and mixed epithelial borderline tumours were rare lesions. Twenty one patients (68%) presented in Stage-la. Surface growth correlated with recurrences. The prognosis remained good in serous borderline tumours even in the presence of implants as these were non-invasive. The mean disease free survival was 43.03 months. There was no statistical difference in disease free survival of patients with and without implants.     

Cytologic identification of serous neoplasms in peritoneal fluids.

BACKGROUND: Recognition of serous neoplasms in peritoneal fluids and their subclassification into serous borderline tumors (SBT) and serous carcinomas (SCA) may be difficult. The objective of this study was to determine whether morphologic criteria can distinguish reactive mesothelial cells (RM), SBT, and SCA (grades 1-3) in peritoneal fluids. METHODS: A blinded review of 42 peritoneal fluids from 40 patients with histologically confirmed RM (n = 10 patients), SBT (n = 7 patients; 3 with primary ovarian tumors and 4 with primary peritoneal tumors), and SCA (n = 23 patients; 7 with grade 1 tumors, 6 with grade 2 tumors, and 10 with grade 3 tumors; 12 with primary ovarian tumors and 11 with primary peritoneal tumors) evaluated papillae presence and size, intercellular windows, group contours, dyshesion, nuclear atypia, size and overlap, cell size, and nucleoli and nuclear-to-cytoplasmic ratios. From these parameters, specimens were classified as RM, SBT versus grade 1 SCA, or grade 2 SCA versus grade 3 SCA. RESULTS: RM were identified as groups of small cells with minimal nuclear atypia and overlap, intercellular windows, and irregular group borders without papillae. No features differentiated SBT from grade 1 SCA. Grade 2 and 3 SCA showed more nuclear atypia and overlap with larger nuclei and cells. Thirty-nine of 42 specimens (95%) were correctly identified as RM or serous neoplasm. Two SBT specimens and one grade 1 SCA specimen were overcalled, and three SCA specimens (two grade 2 and one grade 3) were undergraded. CONCLUSIONS: The distinction of RM from serous neoplasms in peritoneal fluids is possible in most patients by examination of cell group architecture, nuclear atypia, and nuclear size. Differentiation of SBT from grade 1 SCA is not reliable, meriting a differential diagnosis. Most high-grade SCA specimens can be identified by increased nuclear atypia, overlap, and size.