Disagreement of histopathological diagnosis of different pathologists in ovarian tumors-with some theoretical considerations

Identifying transcriptomic correlates of histology using deep learning

Linking phenotypes to specific gene expression profiles is an extremely important problem in biology, which has been approached mainly by correlation methods or, more fundamentally, by studying the effects of gene perturbations. However, genome-wide perturbations involve extensive experimental efforts, which may be prohibitive for certain organisms. On the other hand, the characterization of the various phenotypes frequently requires an expert's subjective interpretation, such as a histopathologist's description of tissue slide images in terms of complex visual features (e.g. 'acinar structures'). In this paper, we use Deep Learning to eliminate the inherent subjective nature of these visual histological features and link them to genomic data, thus establishing a more precisely quantifiable correlation between transcriptomes and phenotypes. Using a dataset of whole slide images with matching gene expression data from 39 normal tissue types, we first developed a Deep Learning tissue classifier with an accuracy of 94%. Then we searched for genes whose expression correlates with features inferred by the classifier and demonstrate that Deep Learning can automatically derive visual (phenotypical) features that are well correlated with the transcriptome and therefore biologically interpretable. As we are particularly concerned with interpretability and explainability of the inferred histological models, we also develop visualizations of the inferred features and compare them with gene expression patterns determined by immunohistochemistry. This can be viewed as a first step toward bridging the gap between the level of genes and the cellular organization of tissues.

The management of borderline epithelial tumors of the ovary

The histopathological diagnosis and treatment of borderline epithelial tumors of the ovary (BTO) still pose problems to both pathologists and gynecologists. BTO is a disease of younger, fertile females and generally has an excellent prognosis. A minority of patients, however, succumb to this disease. A review of the literature is given addressing aspects of epidemiology, histology, treatment and prognosis, resulting in a proposal for the management of serous and mucinous borderline tumors of the ovary.

Randomized study on adjuvant chemotherapy in stage I high-risk ovarian cancer with evaluation of DNA-ploidy as prognostic instrument

PURPOSE

Adjuvant chemotherapy versus observation and chemotherapy at progression was evaluated in 162 patients in a prospective randomized multicenter study. We also evaluated DNA-measurements as an additional prognostic factor.

PATIENTS AND METHODS

Patients received adjuvant carboplatin AUC 7 every 28 days for six courses (n = 81) or no adjuvant treatment (n = 81). Eligibility included surgically staged and treated patients with FIGO stage I disease, grade 1 aneuploid or grade 2 or 3 non-clear cell carcinomas or clear cell carcinomas. Disease-free (DFS) and disease-specific (DSS) survival were end-points.

RESULTS

Median follow-up time was 46 months and progression was observed in 20 patients in the treatment group and 19 in the control group. Estimated five-year DFS and DSS were 70% and 86% in the treatment group and 71% and 85% in the control group. The hazard ratio was 0.98 (95% confidence interval (95% CI): 0.52-1.83) regarding DFS and 0.94 (95% CI: 0.37-2.36) regarding DSS. No significant differences in DFS or DSS could be seen when the log-rank test was stratified for prognostic variables. Therefore, data from both groups were pooled for the analysis of prognostic factors. DNA-ploidy (P = 0.003), extracapsular growth (P = 0.005), tumor rupture (P = 0.04), and WHO histologic grade (P = 0.04) were significant independent prognostic factors for DFS with P < 0.0001 for the model in the multivariate Cox analysis. FIGO substage (P = 0.01), DNA ploidy (P < 0.05), and histologic grade (P = 0.05) were prognostic for DSS with a P-value for the model < 0.0001.

CONCLUSIONS

Due to the small number of patients the study was inconclusive as regards the question of adjuvant chemotherapy. The survival curves were superimposable, but with wide confidence intervals. DNA-ploidy adds objective independent prognostic information regarding both DFS and DSS in early ovarian cancer.

Prognostic value of flow cytometric deoxyribonucleic acid index in endometrial carcinoma: comparison with other clinical-pathologic parameters

OBJECTIVE

The aims of the current study were to verify the impact of flow cytometric deoxyribonucleic acid index on clinical outcome in endometrial carcinoma and to assess whether its value is independent from the other clinical-pathologic features.

STUDY DESIGN

In a prospective series 74 cases of endometrial carcinoma with surgery performed at our institution were studied. Flow cytometry was performed on fresh tumor samples. The median follow-up period was 31 months (range 8 to 52). Disease-free survival and actuarial survival were the end points of the study.

RESULTS

Among the 74 patients (53 with diploid and 21 with aneuploid tumors) there were 14 recurrences and 10 deaths caused by the disease. The recurrence rate was 7.5% for the diploid and 47.6% for the aneuploid tumors (p < 0.001). Mortality was 3.8% for diploid and 38% for aneuploid cases (p < 0.001). Disease-free survival was 89.1% in the former group and 36.3% in the latter. Actuarial survival (Kaplan-Meier method) was 94.7% and 49.5%, respectively. Deoxyribonucleic acid index, stage (International Federation of Gynecology and Obstetrics), and grade of differentiation were significantly correlated with survival, whereas age, depth of myometrial invasion, and histologic type were not. In a multivariate analysis (Cox proportional hazards) deoxyribonucleic acid index was the strongest independent predictor of clinical outcome, followed by International Federation of Gynecology and Obstetrics stage, whereas grade of differentiation yielded no independent prognostic information.

CONCLUSIONS

The flow cytometric deoxyribonucleic acid index is an important independent prognosticator, and its determination should be included in the standard management of endometrial cancer.

The prognostic value of clinical, pathologic, and biologic parameters in ovarian cancer

BACKGROUND

The prognosis in ovarian cancer remains poor, and there is a need to identify patients who are less likely to respond to treatment.

METHODS

In a study of 133 unselected patients with ovarian adenocarcinoma treated by a standard protocol, variables such as age, tumor type, International Federation of Gynecology and Obstetrics stage, cellular differentiation, amount of residual disease after surgery, and results from flow cytometry were correlated with survival and relapse at 24 months.

RESULTS

Although stage and cellular differentiation were found to be significant associations with survival and relapse, multivariate analyses identified only residual disease and ploidy status (and the related DNA index and percentage of aneuploid cells) as independent prognostic variables. The magnitude of the effect of ploidy depended on the amount of residual disease; among patients with less disease (< 2 cm), the mortality rate was nearly fourfold higher for those with aneuploid tumors than for those with diploid tumors.

CONCLUSIONS

Routine use of ploidy determination in ovarian cancer is an important prognostic indicator, especially for a subgroup of patients with minimal residual disease.

Comparison between flow cytometry and image cytometry in ploidy distribution assessments in gynecologic cancer

The DNA content in 37 tumors from 34 women with gynecological cancer was measured by flow cytometry (FCM) and interactive image cytometry (ICM). Agreement was obtained in 81% of cases as regards ploidy levels, but seven tumors (19%) showed different ploidies. Of these, five were classified as diploid by FCM but either aneuploid (three cases) or polyploid (two cases) by ICM. Two other tumors were aneuploid by ICM but polyploid (one case) and unclassifiable (one case) by FCM. All tumors classified as aneuploid by FCM were also aneuploid by ICM, and all tumors classified diploid by ICM were also diploid by FCM. Of six patients whose tumors were classified as euploid (five diploid and one polyploid) by FCM but classified as aneuploid by ICM, five relapsed, and three of these have died of disease. On the basis of these findings, it is concluded that ICM must be performed in cases classified as diploid by FCM to ensure that small subpopulations of aneuploid tumor cells are not overlooked.

The diagnosis of ovarian cancer by pathologists: how often do diagnoses by contributing pathologists agree with a panel of gynecologic pathologists?

The Cancer and Steroid Hormone Study, a multicenter, population-based, case-control study of ovarian, breast, and endometrial cancer in women 20 to 54 years of age, permitted the diagnoses of contributing pathologists to be compared with those of a panel of three gynecologic pathologists. A diagnosis of ovarian cancer was made by contributing pathologists on 477 subjects. Agreement between the two groups of pathologists was 97% for primary epithelial ovarian cancer and 89% for primary nonepithelial ovarian malignancies. Agreement on diagnosis of major cellular subtypes of ovarian malignancy ranged between 73% for endometrioid cancer and 100% for clear cell carcinomas. We conclude that the diagnosis of pathologic features of primary ovarian cancer is highly predictable. Nonetheless, diagnosis by histologic type varies sufficiently that a review process should be considered for clinical or investigative decisions involving specific histologic diagnoses of ovarian cancer.

Prognostic significance of tumor ploidy in patients with advanced ovarian carcinoma

Fresh tumor specimens obtained from 53 consecutive patients with FIGO Stage III ovarian carcinoma were analyzed by flow cytometry. All patients were treated by a standard protocol: maximal tumor excision and cisplatin/cyclophosphamide/adriamycin chemotherapy, and followed-up for at least 24 months. Thirty-two percent of tumors were diploid (DNA index = 1.00) and 68% aneuploid (DNA index greater than 1.00), with more aneuploid tumors being associated with larger residual tumor and poor cellular differentiation. Patients with diploid tumors were found to survive significantly better than those with aneuploid tumors, in terms of survival rate (65% versus 31%), median survival time (33 months versus 13 months), and mean disease-free interval (17.8 months versus 8.2 months). The influence of the amount of residual tumor after primary surgery on survival was only significant in patients with diploid tumors. Our results support previous findings that tumor ploidy is an important prognostic indicator in ovarian cancer. We found aneuploidy to be associated with a poorer clinical outcome in Stage III disease, regardless of the amount of residual tumor after primary surgery and the degree of cellular differentiation.

DNA flow cytometry, clinical and morphological parameters as prognostic factors for advanced malignant and borderline ovarian tumors

Patients with malignant ovarian (n = 111) and borderline (n = 8) tumors (FIGO stage III/IV) underwent surgery and chemotherapy and were analyzed clinically (age, residual tumor after surgery) and morphologically (type, grade, psammoma body content), and by means of flow cytometry (DNA ploidy, S-phase fraction). Follow-up was 12-72 months for investigation of survival. Patients under 60 years of age (n = 18) with malignant tumors showed longer survival than patients over 60 (n = 93) (P = 0.078). Residual tumor was relevant for prognosis in malignant tumors only if macroscopically there was no residual disease (n = 13). There were no significant differences between residual tumors less than or equal to 2 cm (n = 61) and greater than 2 cm (n = 37). WHO typing was of little importance for survival analysis. Compared to borderline tumors (n = 8), serous (n = 65), endometrioid (n = 13), nonclassifiable (n = 12), mucinous carcinomas (n = 8), and nonepithelial tumors (n = 12) had a poor prognosis. Psammoma bodies were found in 25 patients with serous carcinomas, 7 of them had a high content. The prognosis for these 7 patients was much better than that for patients with a moderate or low psammoma body content (P = 0.006). Twenty-three epithelial tumors were graded G1, 28 were G2, and 47 were G3. However, grading was considered only as a prognostic factor in serous carcinomas (n = 65) (P = 0.028). A total of 199 DNA histograms from 119 patients were analyzed by flow cytometry (FCM). There were no correlations between tumor type and DNA ploidy or S-phase fraction. Seven of eight borderline tumor and all serous carcinomas with a high content of psammoma bodies were diploid combined with a low (less than or equal to 4%) S-phase fraction. DNA ploidy and S-phase fraction were excellent prognosticators. Of 99 epithelial malignant tumors, 35 were diploid and 64 were aneuploid. An S-phase fraction less than or equal to 4% was found in 39 patients, 4.1-10% in 73 patients, and greater than 10% in 23 patients. Diploid tumors and tumors with a low S-phase fraction showed the best survival (P = 0.007, resp. 0.0001). Our study emphasizes the importance of an accurate histology, including information on psammoma body content, and the importance of DNA flow cytometry. The advantage of FCM is that the results are simple, reproducible, and objective.

Possibilities and progress of quantitative pathological examination of ovarian tumours

Morphometric and flow DNA-cytometric analysis of ovarian tumours of the common epithelial type has an important and strong additional prognostic impact, which is stage-independent, and more important than subjective grade. In stage I cancers, combined morphometric analysis and DNA index assessed with flow-cytometry can indicate a subgroup of patients with an especially poor prognosis. In stage III and IV cancers, morphometric features exceed the prognostic value of cellular DNA content, as far as they allow selection of a small subset of patients with an excellent prognosis. These results indicate that quantitative pathological examination is of essential importance for therapeutic decision-making both in early and late ovarian cancer patients, and therefore should be carried out as a routine procedure in women with this disease.

Observer variation in histologic classification of malignant and borderline ovarian tumors

Eight hundred sixty-nine primary malignant or borderline ovarian tumors reported to the Norwegian Cancer Registry were reviewed. The histologic slides were randomly distributed to six observers and classified according to the World Health Organization classification of ovarian tumors. By rotation of slides, each tumor was successively reviewed by three observers. Each observer was given approximately 40 duplicates of slides he or she had typed before, mixed in with the slides for the third review. A contracted version of the classification with 27 entries was used in the analysis. Mean intraobserver reproducibility was 62% (kappa, 0.53), varying from 50% to 75% (kappa, 0.34 to 0.70) for the individual observers. The mean rate of agreement between two observers was 56% (kappa, 0.46), varying from 46% to 65% for the individual pairs of observers. The rate of full agreement among three observers was 41%. The most common disagreements were between different specific types of carcinoma, between undifferentiated and differentiated carcinoma, between borderline and malignant tumors, between unclassified and classified carcinoma, and between mixed and pure types of carcinoma. Very low reproducibility was obtained for mixed and unclassified carcinoma.

Prognostic value of the flow cytometric DNA index in human ovarian carcinoma

Flow cytometric measurements were done on 51 ovarian carcinoma specimens collected from consecutive patients in a prospective study. The ploidy status was related to the course of the disease. The tumors from 26 (52%) of 50 evaluable patients had DNA aneuploidy. Patients with diploid tumors were more often considered disease-free after initial operation (P less than 0.01). Patients with aneuploid tumors had a more aggressive course of the disease in all respects of comparison. The median survival of patients with diploid tumors was 18 months as compared to 8 months for those with aneuploid tumors (P less than 0.0005). Flow cytometric DNA measurements give important prognostic information and such analyses should be included in future clinical trials. Through the development of high-speed instrumentation they also may become feasible in routine clinical work.

Prognostic factors in borderline and invasive ovarian tumors of the common epithelial type

Present reports show that surgical factors, response to therapy and histological criteria are important for predicting the prognosis of patients with common epithelial types of ovarian tumors. Newer techniques such as morphometry, DNA cytometry, immunological and immunopathological techniques may help to define prognostic factors even more accurately. As a result, these recently developed methods may enhance the value of well-established classical predictors of the outcome in case of borderline or invasive ovarian tumour.

Ploidy assessment of benign and malignant ovarian tumors by flow cytometry. A clinicopathologic study

In a prospective study, 112 fresh ovarian tumor samples were collected from 83 consecutive patients. Cellular DNA content was measured by flow cytometry. All the benign (n = 24) and semimalignant (n = 6) tumors were diploid. Of 50 malignant tumors, 24 (48%) were diploid and 26 (52%) were aneuploid. Aneuploidy was more frequent in the advanced stages of the disease, in tumors of low degree of differentiation, and in older patients. The patients with aneuploid tumors had smaller primary tumors and more often ascites. The fraction of cells with S-phase DNA content was higher in the aneuploid tumors. No association was seen to the tumor type. Ploidy determination is objective and reproducible. Aneuploidy associates to most negative prognostic factors in ovarian carcinoma and may reflect the aggressiveness of the tumor. The ploidy status may be taken into consideration in the stratification of patients of comparable risk for treatment studies.

Quantification of epithelial volume by image processing applied to ovarian tumors

This paper describes an image analysis technique for automated estimation of the percentages of epithelium and stroma in (tumor) tissue. The program is evaluated on ovarian tumors of the serous, mucinous, and endometrioid type. From standard paraffin sections, stained with pararosanilin Feulgen and naphthol yellow, a blue-yellow image pair was recorded. The blue image was used for the determination of the total tissue area and the yellow image for the epithelial area. For the latter the image processing method is based on the fact that epithelial nuclei are generally more tightly packed than stromal nuclei. A structural approach was applied, in which the segmentation of the nuclei was based on the image contrast range in the density domain. The method has been tested with 78 image pairs from 19 ovarian tumors with varying degrees of malignancy. The area percentages, as assessed with image processing, were strongly correlated to control percentages, established by interactive morphometry (r = 0.98).

The prognostic variability of ovarian tumor grading by different pathologists

In a multicenter ovarian tumor study, it was shown that there are considerable differences between different pathologists when grading the same ovarian tumors. The question arises whether these differences in grading also reflect prognostic differences. To investigate this, the survival curves of the various tumor grades assigned to the same tumors by four different pathologists were investigated. The results of the present study indicate that tumor grade was strongly correlated with the prognosis, although there were considerable variations in the survival curves and in the five year survival of patients of the same grade assessed by the different pathologists. Five-year survival varied from 82 to 100% in the borderline tumors, from 49 to 80% in the well, and from 21 to 48% in the moderately differentiated tumor groups. Only the poorly differentiated cancers showed less variation. Similar interobserver differences were found in the histological typing and (strictly predefined) malignancy grades. The intraobserver variation, which was also tested after a 6-month interval, was somewhat lower, but was still present for each of the pathologists. These data clearly indicate the necessity for objective, sharply defined, reproducible criteria rather than subjective grades.

DNA flow cytometry, histological grade, stage, and age as prognostic factors in human epithelial ovarian carcinomas

The prognostic value of parameters as determined by DNA flow cytometry, in combination with other parameters, was assessed in 75 patients with ovarian carcinomas (20% in stage I and II). DNA- index of the tumours appeared to predict mainly the degree of differentiation, since the DNA-index only tended to affect prognosis and low grade tumours were mainly diploid. However, with ascites a non-diploid DNA-index was associated with a significantly lower survival in short-term follow-up. Subgroups with a favourable prognosis were defined by an age of patients less than or equal to 40 years, grade 1 tumours, and tumours in stage I or II. Particularly favourable was the combination of a grade 1 tumour, or a tumour in stage I or II, with percentage of cells in G1 greater than 85%. Prognostically poor subgroups were defined by an age greater than 60 years, by grade 2 or 3 tumours and by a clinically advanced stage. The combination of grade 2 or 3, or a clinically advanced stage, with G1-phase fraction less than or equal to 85% identified subgroups with a particularly poor prognosis.

Flow cytometric deoxyribonucleic acid index: a prognostic factor in endometrial carcinoma

In a prospective study, flow cytometric deoxyribonucleic acid analyses were performed on cell samples from benign and malignant tumors of the endometrium and benign endometrium. No ploidy aberrations were found in normal endometrium. Of 52 cases with adenocarcinomas, 38 (73%) were diploid and 14 (27%) aneuploid. Both the frequency and the degree of aneuploidy were correlated to histologic tumor grade but not to other prognostic variables such as International Federation of Gynecologists and Obstetricians stage, depth of myometrial invasion, or patient age. Patients with aneuploid tumors had a higher recurrence rate and shorter disease-free intervals as compared to those with diploid tumors. Similarly, death rates were higher and the median survival was shorter in the aneuploid group. Flow cytometric ploidy determination may therefore serve as an important prognostic parameter.

Mucosubstances in classification of serous and mucinous ovarian tumors: a morphometrical study

108 serous and 106 mucinous ovarian cystadenomas of varying malignancy were studied with the saliva-periodic acid-Schiff (SPAS) reaction and with the Alcian blue (AB) pH 2.7 method, which stain neutral and acid mucosubstances, respectively. Positively stained mucin was quantitated morphometrically and the measured parameters were tested by discriminant analysis. As expected, the mucinous tumors were more positive for mucin than the serous ones. Also the borderline tumors contained more mucin than their benign or malignant counterparts. The best discriminating capacity for mucin was obtained in serous tumors with the AB stain and in mucinous tumors with the SPAS reaction. The ratio of neutral to acid mucosubstances decreased in mucinous cystadenomas with increasing malignancy.

The value of morphometry to classic prognosticators in breast cancer

In 271 breast cancer patients with adequate follow-up for at least 5.5 and maximally 12 years, the value of morphometry to classic prognosticators of breast cancer (tumor size and axillary lymph node status) was assessed. Previous studies had indicated the value of this quantitative microscopic technique. Apart from quantitative microscopic features, subjective qualitative features such as nuclear and histologic grade were assessed as well. Univariate life-table analysis showed the significance (p less than 0.001) of several features such as lymph node status, tumor size, nuclear and histologic grade, and several morphometric variables (mitotic activity index, mean and standard deviation of nuclear area). Cellularity index was also significant (p = 0.02). Survival analysis with Cox's regression model, using a stepwise selection as well as backwards elimination, pointed to three features: mitotic activity index, tumor size, and lymph node status. Mitotic activity was the most important prognostic feature, but the combination of these three features in a multivariate prognostic index had even more prognostic significance. Kaplan-Meier curves showed that the 5-year survival of lymph node-negative patients (n = 146) is 85%, versus 93% in patients with a "good prognosis index" (n = 150). For lymph node-positive patients (n = 125), 5-year survival was 55%, compared with 47% in the "high index" (poor prognosis) patients (n = 121). Logistic discriminant analysis with 5.5-year follow-up as a fixed endpoint (191 survivors and 80 nonsurvivors) essentially gave the same results. Application of two instead of one decision threshold (e.g., numerical classification probability 0.60 and 0.40) decrease the number of false-negative and false-positive outcomes, however, with a number of patients falling in the class "uncertain." Thus, in agreement with other studies, morphometry significantly adds to the prognosis prediction of lymph node status and tumor size. Mitotic activity index is the best single predictor of the prognosis. An additional index advantage is that the multivariate model results in a continuous index variable that can be subdivided in many classes with an increasing risk of recurrence, so that more refined clinical therapeutic decision making is possible in individual patient care. The morphometric techniques are inexpensive and fairly simple and therefore can be applied in most pathology laboratories.

The reproducibility of a quantitative grading system of bladder tumours

In order to test the reproducibility of a histomorphometrical grading system of bladder tumours, 15 tumours were twice measured independently by three pathologists. The data obtained were then analysed and compared with that of histological grading only. The way in which these morphometrical results are presented to the clinician in a computerized report is described. The need for a satisfactory reliable reproducibility test of every histomorphometrical grading system before introduction in diagnostic pathology is discussed.

Combined morphologic and cytochemical grading of serous ovarian tumors

The potentiality of DNA analysis to complement morphologic evaluation in classifying serous ovarian tumors as adenoma, borderline malignancy, or invasive adenocarcinoma was investigated in a series of 54 tumors. The DNA analyses were performed on histologic tumor sections. The primary diagnoses were borderline tumor in 24 cases and invasive adenocarcinoma in 30 (World Health Organization classification). When the specimens were reviewed, 17 of the 54 tumors were reclassified, after which the series consisted of 9 adenomas, 24 borderline tumors, and 21 invasive adenocarcinomas. Rising histologic malignancy grade was associated with increasing numbers of cells showing high DNA content. The DNA levels in the adenomas thus were within the diploid range of a normal cell population. They were somewhat higher in the borderline tumors and were highest in the invasive adenocarcinomas. Though no clear-cut intergroup demarcation was discernible, there was a subgroup of adenocarcinomas with greatly elevated DNA levels, indicating high biologic malignancy. The observations suggested that DNA analyses can complement histologic malignancy grading and can be useful for the recognition or highly malignant tumors among invasive adenocarcinomas.

Basic points in and practical aspects of the application of diagnostic morphometry

The number of applications of diagnostic morphometry is rapidly increasing. We have routinely used this technique for more than four years in our laboratory. Essential points in the application are: the type of lesions to which it is applied, multivariate analysis instead of single variate analysis and selection by a skilled pathologist of the relevant microscopical features. Such selective morphometry is useful in up to four percent of the total material entering an average pathology laboratory; in teaching laboratories the percentage may be considerably higher (e.g. 10-12%). Most of the applications are found in tumourpathology, but applications in non-tumor pathology are also promising. It is expected that diagnostic morphometry will become widely available and accepted in the next three to five years. Special symposia, diagnostic courses and organization of interested pathologists within the framework of the diagnostic morphometry workgroup of the European Society of Pathology is expected to be of help in this direction. Highly automatic, yet interactive, methods will become available within the next five to ten years. Further acceptance of these methods in most laboratories by 1990 is likely. A modular setup of quantitative microscopy equipment therefore is advisable. Turn-key, dedicated instruments for well-defined diagnostic problems are another (future) possibility. The diagnostic morphometry process as a product requires support and quality control. The pathologist is responsible for this and diagnostic morphometry should be seen as an integrated part of the diagnostic process.

Borderline or malignant ovarian tumour? A case report of decision making with morphometry

A young woman presented with bilateral ovarian tumours. Multiple sections of each tumour were shown to many pathologists for consultation; some considered the tumours to be borderline, whereas others thought that one or both of them was malignant. Morphometry showed that the numerical classification probabilities for borderline tumour were 0.78 for the left ovarian tumour and 0.85 in the right. The lesions were therefore regarded as borderline tumours and no additional chemotherapy was given. Three years after the second operation the patient is alive and well without clinical or biochemical evidence of recurrence. Most patients with borderline tumours who die from the disease do so in the first two years after the operation. This young patient was prevented from severe overtreatment by the application of morphometry, illustrating its use in this area of diagnostic gynaecopathology.

Interobserver variability in the interpretation of epithelial ovarian cancer

The interobserver diagnostic reproducibility for epithelial ovarian neoplasia was studied. The histologic sections of 68 ovarian tumors from 34 patients were independently reviewed by two pathologists from different institutions, without knowledge of the clinical course. Each observer rendered 68 diagnoses. The interobserver agreement rate for histologic type was 60% and for histologic grade 66%. In the 23 instances in which a discrepancy in grade occurred, 5 (23%) were disagreements in the diagnosis of borderline versus malignant tumors. On analysis of the diagnostic variability with regard to histologic type, one observer (A) classified 60% of the tumors as undifferentiated, while the other observer (B) classified 59% of the tumors as serous. In an attempt to understand the reasons for the diagnostic disagreements, the observers were asked to simultaneously reexamine the material. This occurred 6 months after the initial review and they were unaware of their original diagnoses. The diagnostic differences with regard to histologic type were mainly due to (1) tumor cell heterogeneity, and (2) difficulty in discriminating between serous and undifferentiated tumors. The differences in grade were largely related to the use of different criteria. Observer A used mitotic counts while observer B used glandular pattern and its replacement by solid sheets of epithelium. Observer B consistently assigned a higher grade to the tumors. In making therapeutic decisions, clinicians should be aware of the interobserver diagnostic variability and the reasons for this variability.