Quality control in histopathology and diagnostic cytology

Survey of Performance of Cervical Cytopathology Laboratories and of Screening Programs in Italy

Structure, performance, management, quality control and participation in screening programs of cervical cytology laboratories have been evaluated through a questionnaire sent to all public Italian hospitals, relevant university departments and senior members of relevant scientific associations. Completed questionnaires were received from 276 centers, which gives a response rate of 73%. In this report we concentrate on the need for improvement, but there are a number of centers who have all or almost all the features traditionally associated with good or excellent practice. The main results of the survey are the following. Most of the centers examine relatively few cervical smears, so their workload could be considered too low for maintaining a good level of practice. Six centers examine 3 specimens per woman, about 25% examine 2 specimens, and the rest only 1 specimen. There is a marked variability in filing and storing practices of positive and negative smears and results. Internal quality control is inadequate in most centers, and external quality control is limited to voluntary exchange of dubious or interesting smears. Only half of the centers are involved in screening programs. In 75% of the programs the suggested screening interval is 1 year or even 6 months; only 7 (4.5%) agree with the UICC/ IARC recommended interval of 3 years. The target population coverage varies from 10% to 85%, and it is less than 50% in 78% of the programs. Only 6 programs have an active women's call system. The survey has confirmed the need for launching a national program of internal and external quality control. Almost all centers have expressed their interest to take part.

An assessment of the operation of an external quality assessment (EQA) scheme in histopathology in the South Thames (West) region: 1995-1998

AIMS

To describe the design and organisation of a voluntary regional external quality assessment (EQA) scheme in histopathology, and to record the results obtained over a three year period.

METHODS

A protocol is presented in which circulation of EQA slides alternated with teaching sessions. Procedures for the choice of suitable cases, evaluation of submitted diagnoses, and feedback of results to participants are described. The use of teaching sessions, complementary to the slide circulations, and dealing with current diagnostic problems is also outlined.

RESULTS

Participation rates in the nine slide circulations varied between 66% and 89%, mean 85%. Overall scores were predictably high but 4% of returns, from 10 pathologists, were unsatisfactory. These low scores were typically isolated or intermittent and none of the participants fulfilled agreed criteria for chronic poor performers.

CONCLUSIONS

This scheme has been well supported and overall performances have been satisfactory. The design was sufficiently discriminatory to reveal a few low scores which are analysed in detail. Prompt feedback of results to participants with identification of all "incomplete" and "wrong" diagnoses is essential. Involvement of local histopathologists in designing, running, and monitoring such schemes is important.

Morphometric applications in anatomic pathology

The components of the cell and tissue changes in many diseases are variable and can therefore be quantified. Characterization of these quantitative changes provides data that is useful not only for making a definitive, cell- and tissue-based diagnosis of disease, but also for predicting the course of disease. The spectrum of changes found in malignant tumors, ie, cell grade, architecture, cellularity, extent of invasion, nature and extent of inflammatory reaction, exemplify this range of quantifiable features. The diagnosis and prognosis of nonneoplastic diseases, ie, myopathy and metabolic bone disease, can also be determined by quantitating tissue changes. Morphometry is the quantification of changes in the "objects" of tissues, ie, cells and organelles, and their organization, using quantitative evaluation tools. The principles of morphometry have been known for a century. With the increasing availability of affordable, powerful computer systems and increasingly flexible and user-friendly software has come easier ability to measure these changes. This article discusses the principles of morphometry with illustrations of types of analysis (ie, area fraction, object counting, shape and size analyses, and mutliparametric analyses) using examples of these applications with discussions of error sources and limitations of morphometry.

An analysis of interobserver recognition of the histopathologic features of dysplastic nevi from a mixed group of nevomelanocytic lesions

BACKGROUND

The diagnostic criteria for the histopathologic recognition of the dysplastic nevus are defined, but difficult to apply in practice. However, the use of skin biopsy is on the increase to search for this nevus because of a possible role in melanomagenesis.

OBJECTIVE

The aim was to determine the degree of observer reproducibility in the detection of histologic nevomelanocytic dysplasia as measured across multiple observers and to test whether each observer was precise over a wide sample population. A second aim was to gain some measure of the threshold a person has for such lesions.

METHODS

Histologic specimens from 50 coded nevomelanocytic tumors, which included a group of dysplastic nevi, were independently read by five observers in a blinded fashion. At study completion, the same 50 cases were read again by a melanoma reference pathologist and results analyzed by Cohen's kappa to assess agreement and interobserver variation.

RESULTS

Corrected rates of agreement for dysplastic nevi ranged from 0.32 to 0.71.

CONCLUSION

Continued study and experience are required for precision and reproducibility in the histologic recognition of dysplastic nevi.

An inter-observer and intra-observer variability study on the diagnosis of lymph node biopsy specimens

One hundred lymph node biopsy specimens were examined on two separate occasions by seven pathologists differing in experience in lymphoreticular pathology. Neither history nor immunohistochemistry was provided and the study, therefore, focused on morphological interpretation alone. The participants evaluated each case using a constructed response form in which the confidence with which they entered each response was also entered. Agreement on various points, between pathologists, between the two rounds, and with the referring centre was assessed. Whilst there was a high level of agreement over a diagnosis of benign vs. malignant and non-Hodgkin lymphoma vs. Hodgkin's disease, there was considerably less agreement over both T vs. B cell phenotype and high vs. low grade. The lack of agreement over grade, an evaluation which is usually made independent of immunohistochemistry, is particularly important, because of the relevance to selection of treatment. Proliferation markers may be more appropriate determinants of treatment choice.

Medullary carcinoma of the breast, proposal for a new simplified histopathological definition. Based on prognostic observations and observations on inter- and intraobserver variability of 11 histopathological characteristics in 131 breast carcinomas with medullary features

In a previous study of 131 breast carcinomas with medullary features, we evaluated the diagnostic inter- and intraobserver variation and its prognostic implications using the criteria of typical (TMC) and atypical (AMC) medullary carcinoma of the breast put forward by Ridolfi et al. (1977). We found a considerable interobserver variation as well as intraobserver variation, with significant implication on prognosis, and concluded that the histopathological definition of MC must be sharpened and simplified in order to increase the diagnostic reproducibility. In the present study of the same population of 131 patients with breast carcinomas with medullary features we have examined inter- and intraobserver variation concerning 11 histopathological characteristics. Furthermore, we have analysed the prognostic importance of these 11 histopathological features, and the prognostic implications of the observed inter- and intraobserver variation. Based on the observations, we have eliminated criteria with poor inter-/intraobserver agreement as well as those implying no or minimal impact on the prognosis. We propose a new simplified histopathological definition of medullary carcinoma of the breast (MC), retaining reproducible, prognostically significant criteria (syncytial growth pattern and diffuse, moderate or marked mononuclear infiltration). The prognosis of MC, based on this definition, is significantly better than those of infiltrating ductal carcinomas grade II + III.

Inter- and intraobserver variability in the histopathological diagnosis of medullary carcinoma of the breast, and its prognostic implications

One hundred thirty-one breast carcinomas with medullary features, registered in the Danish Breast Cancer Cooperative Group from 1977-1982, have been histopathologically reviewed by two senior pathologists and classified as typical medullary carcinoma (TMC), atypical medullary carcinoma (AMC), and non-medullary carcinoma (NMC). Diagnostic criteria were based on those put forward by Ridolfi et al. and Fisher et al. The procedure was repeated with an interval of about one year by both pathologists. The diagnostic interobserver agreement was 72% with a Kappa of 0.55. The intraobserver agreement was 77% and 63% with Kappa values of 0.64 and 0.44, respectively. To see whether the observed inter- and intraobserver variability had any prognostic implications, diagnostic subgroups for both pathologists were analyzed with Kaplan Meier plots for recurrence-free survival (RFS) and with log rank tests. In the first evaluation pathologist 1 segregated a group of TMC with a significantly better RFS than for the NMC group, and pathologist 2 segregated a group of TMC with a corresponding strong trend. These findings could not, however, be reproduced in the second evaluation. The study indicates that the criteria of TMC and AMC as proposed by Ridolfi et al. need to be sharpened and simplified in order to reduce inter- and intraobserver variability. Larger studies with a control group of infiltrating ductal carcinomas are mandatory to elucidate the clinical importance of the diagnoses of Typical and Atypical Medullary Carcinoma of the breast.

Percutaneous fine needle aspiration of pulmonary mass lesions--a critical examination of the accuracy of cell typing of malignant tumours

All the biopsies of pulmonary mass lesions obtained by percutaneous needle aspiration over a seven year period were reviewed. Emphasis is laid upon the differences in cell typing of malignant tumours when two types of preparation of the same tissue, cytological smears and tissue sections are examined. Some problems in cell typing are discussed and suggestions for improved proficiency are made.

Quality assessment in cervical cytology: a pilot study

A pilot study of an external quality assessment scheme was run between February 1985 and September 1986 to (i) assess the feasibility of running one from a district general hospital; (ii) to estimate the time required to organise and run it with a computer; (iii) to provide sound statistical results with which future schemes could be compared. Seven laboratories participated, and the 20 smears selected from each laboratory were circulated in three rounds in batches of seven, seven, and six according to a prearranged order. Results analysed using the kappa statistic showed moderate levels of interlaboratory agreement, with complete agreement emerging only on a small proportion of cases.

Quantitative immunocytochemistry by digital image analysis: application to toxicologic pathology

Recent advances in immunocytochemical techniques allow the localization of specific antigens in tissue sections. The work reported here attempts to evaluate the application of antibody-labeled, disease-related protein, followed by microscopy and computerized image analysis. Using an experimental anti-tumor, polyclonal antibody (anti-oncomodulin) as a model, various tissues were prepared for light microscope immunocytochemistry. Sections were incubated with primary antibody, then biotinylated secondary antibody. This was followed by incubation with avidin-biotin-peroxidase (ABC method). Marker was visualized by the presence of precipitated diaminobenzidine. Samples were evaluated using a Zeiss/Kontron IBAS I & II semi-automatic digital image analysis system. Statistical analyses were performed on output data. Results demonstrated the localization and determined optical density of immunolabel. Statistical comparisons showed significant differences between control and experimental sections. The practical application of these combined techniques provides the toxicologic pathologist with a powerful tool for accurate and objective determination of the location and relative amount of selected proteins in normal and abnormal tissues.

A morphometrical analysis of dysplasia in small adenomas of the large intestine

In a morphometrical study of 40 colorectal adenomas less than 10 mm in diameter and of 10 specimens of normal mucosa, it was found that nuclear size, perimeter and shape-factor of the epithelial cells were significantly different in neoplastic when compared with normal tissues. The same was found for the volume fraction of stroma, gland spaces, goblet and non-goblet epithelium, for the gland diameter, nuclear stratification height and stratification index, but not for the epithelial height nor the total volume fraction of the epithelium. In a multivariate analysis, stratification index and nuclear size of the epithelial cells contributed most significantly to determination of the histological grade of dysplasia in adenomas. By the combination of these two morphometric variables 75% of all adenomas could be correctly allocated to the grade of dysplasia.

DNA flow cytometry of histological material from dysplastic lesions of human gastric mucosa

DNA flow cytometry has been carried out on histologically processed human gastric tissue showing varying grades of gastric dysplasia, intramucosal carcinoma and regenerative changes. No cases of DNA aneuploidy were encountered in cases showing regenerative changes or mild or moderate dysplasia. DNA aneuploidy was found in 5/7 cases of severe dysplasia and 3/11 cases of intramucosal cancer. Irregularities of the G0/G1 peak were encountered in a further 18 samples including normal and regenerative gastric mucosa. However these were not thought to indicate DNA aneuploidy. The interpretation of these abnormalities and the affect on the frequency with which DNA aneuploidy is reported in pathological lesions is discussed.

Histopathology reporting of mastectomy specimens--an assessment of inter-hospital variation

The routine histopathological reporting of mastectomy specimens at a typical District general hospital and a London teaching hospital have been reviewed. Deficiencies in the assessment of prognostically important variables were revealed. Ways of improving standards are discussed.

Histopathological systems of breast cancer classification: reproducibility and clinical significance

The inter- and intraobserver reproducibilities of the histopathological systems of breast cancer classification suggested by the World Health Organisation (WHO), the Armed Forces Institute of Pathology (AFIP) and Ackerman have been analysed. The reproducibilities of the three classification systems were only "fair" to "moderate" and no correlation with the five-year recurrence rate was found. Our results indicate that these classification systems are without biological significance and are useless for prognosis in the individual patient. When the tumours were classified according to degree of differentiation (high, moderate, low) or graded according to WHO (which includes both differentiation and nuclear atypia), however, there was a significant correlation with the five-year recurrence rate. Yet even such "reduced" subdivisions are of no value in judging prognosis for the individual patient at the time of diagnosis; rather, they are useful only in the follow-up analysis of groups of patients.

Respiratory cytodiagnosis: study in observer variation and its relation to quality of material

Sensitivity and accuracy of cytodiagnosis were assessed in a multicentre study. Six centres each provided sputum cytological material from 20 cases. Each centre screened and reported on the 100 slides provided by the other five centres. The reports were assessed against consensus reference diagnoses, reached by discussion with transparencies, histological sections, and closed-circuit television. False positive rates of 0-4% (average 1.3%) and false negative rates of 0-12% (average 5.0%) of slides examined were recorded. The order of agreement on the three common cell types was adenocarcinoma 75% (50-91%), squamous cell carcinoma 80% (59-94%) and small carcinoma 95% (71-100%). The effect of quality of material on cytological opinion was assessed by comparing disagreement rates on each of the different sets of 20 slides. Disagreement varied from 1% to 23% depending on which set of material was examined.

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

Microscopical sections of forty-nine ovarian tumors have been assessed as benign, borderline or malignant by four different pathologists, who were unaware of the FIGO stage and clinical follow-up of each patient and each others' diagnosis. There was absolute agreement in 37 cases (75.5%), and disagreement in 12 cases (24.5%). The majority of the disagreements involved borderline-malignant differences. If one of the pathologists did disagree with the other three (in 9 cases, or 18%), there is no correlation between disagreement and histopathological experience. In three cases (6.5%) two pathologists did disagree with the other two. It is concluded that in pathology, objective reproducible and if possible, quantitative techniques should be used instead of subjective grading methods. The probability of the diagnosis should be expressed in a numerical way.

External quality assessment of clinical laboratories in the United Kingdom

A review is given of the National External Quality Assessment Schemes (NEQASs) in various pathology disciplines in the United Kingdom, with a discussion of the relative roles of the DHSS, individual laboratory scientists, and the relevant professional bodies. Principles of operation and scientific problems in the design of NEQASs in different disciplines are described and contrasted, and some comparisons with the experience in other European countries and the USA are drawn.

Quantitation of borderline and malignant mucinous ovarian tumours

Discrimination between borderline and malignant mucinous ovarian tumours is a well-known diagnostic problem. In order to obtain objective reproducible and consistent features for differential diagnosis, 32 quantitative microscopical features were assessed in 10 benign, 10 borderline and 22 malignant mucinous ovarian tumours. There were many significant differences between the three groups, but using multivariate analysis there was 93% agreement between the histopathological assessment of these sections and the qualitative analyses. The following features were useful in the quantitative classification: the mean area, the mean perimeter and the mean of short axis of the nucleus; the volume percentage of the epithelium; the mitotic activity. In three cases, there was a difference between the original histopathological and computer classification. It was debatable whether the original diagnosis was correct, and therefore, all the cases were independently reassessed blind by three pathologists. Their diagnoses lend strong support to the computer classification in two of the three cases. The computer classification seems therefore to be even better than 93%. The present quantitative techniques are inexpensive, relatively easy to use, and, we believe, have a useful place in diagnostic histopathology.

Invasive squamous cell carcinoma of the uterine cervix. II. Reproducibility of a histopathologic malignancy grading system

A histopathologic malignancy grading system for invasive squamous carcinoma of the uterine cervix has previously been presented. The grading results in a total malignancy point value for every patient (range 8-24). This score has been proven to have a significant prognostic value for the individual patient. The inter-observer reproducibility of this system has been examined by two pathologists, on the pretreatment biopsies of 100 patients and the intra-observer reproducibility on 190 patients (observer one) and on 100 patients (observer two). These biopsies were estimated twice and three times, respectively, without knowledge of former results and at an interval of 2 to 6 months. The inter-observer correlation coefficient was 0.54, the intra-observer correlation coefficients 0.94 and 0.74, respectively.