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In the WHO Classification of Tumours of the Urinary System and Male Genital Organs published in 2016, it was officially recommended that the percent of Gleason pattern 4 (GP4) be reported on pathology reports to better reflect the extent in Gleason score 7 tumors. In this study we assessed the reproducibility of reporting GP4 on prostate biopsies. We analyzed prospectively 422 cores containing GP4 from our consult cases over a period of 2.5 months. The percent pattern 4 was assigned to all the cases in 10% increments from 0% to 100% (with the addition of 5%) by 1 of 4 fellows in urological pathology and by the expert urological pathologist. Out of 422 cores, 32% were an exact match and 75% were within ±10% (weighted κ [κW] value 0.67). Cases were further stratified on the basis of (1) scattered versus clustered GP4 in the background of Gleason pattern 3, (2) continuous versus discontinuous tumor involvement, (3) cribriform/glomeruloid pattern only versus poorly formed/fused pattern versus mixed cribriform and poorly formed/fused pattern, and (4) total tumor involvement of the core (≤10% vs. >10% of the core). No significant differences were observed in the first 3 variables. However, in cases with ≤10% involvement of the core, 61% were within ±10% (κW=0.50) compared with cases with >10% involvement of the core, in which 78% were within ±10% (κW=0.70). In summary, we showed that assessment of percent GP4 was relatively reproducible, with substantial agreement within ±10% in cases. However, with

Accurate recognition of Gleason pattern 5 (GP5) prostate adenocarcinoma on needle biopsy is critical as it is associated with disease progression and adverse clinical outcome. Despite important implications of this diagnosis, interobserver variation in the diagnosis of GP5 has not been adequately studied. Digital images of 66 prostate adenocarcinoma cases that potentially contained a GP5 component were distributed to 16 urologic pathologists who were asked to classify whether GP5 was present. Each image was initially classified into 1 of 4 morphologic subpatterns by 2 coauthors (R.B.S. and M.Z.): solid nests (15), comedocarcinoma (8), single cells and/or cords (35), and variant morphology (8). Additional features captured included: size (large:20 cells, medium: 10 to 20 cells, and small:10 cells) and distribution of nuclei (uniform vs. nonuniform) for nests pattern; intraluminal coagulative tumor necrosis, karyorrhectic debris, and amorphous material for comedocarcinoma pattern; and quantity (≤5, 6 to 10, and10) and distribution (clustered vs. intermixed with adjacent well-formed glands) for single cells/cords pattern. Interobserver reproducibility of a diagnosis of GP5 was assessed and the morphologic subpatterns and features were correlated with the consensus diagnosis (defined as 75% agreement). Interobserver reproducibility for overall diagnostic agreement was fair (κ=0.376). Among subpatterns, comedocarcinoma had highest reproducibility (κ=0.499), followed by variant morphology (κ=0.443), single cells/cords (κ=0.369), and nests (κ=0.347). All cases with the following features achieved consensus for GP5: large nests regardless of nuclear distribution; coagulative necrosis with or without karyorrhectic debris; single cells/cords10 or 6 to 10 in a cluster; and signet ring-like cells in single cells or within nests pattern. A majority of cases with the following features achieved consensus against GP5: medium-size nests; exclusive intraluminal amorphous material; single cells/cords ≤5; and Paneth cell change. Remaining morphologic features did not reach consensus for or against GP5. A majority (86%) of participants would diagnose a small focus of GP5 only when it is present in1 level. The diagnostic reproducibility of GP5 within certain morphologies was only fair among urologic pathologists. However, the diagnosis of GP5 was more reproducible when certain restrictive morphologic and quantitative criteria were applied. These findings suggest that additional studies are needed to find highly reproducible features of GP5 associated with documented aggressive clinical outcome.

A worldwide-accepted histologic, classification of the gastric carcinomatous and precancerous lesions is a prerequisite for a consistent recording of epidemiologic data and for both developing and evaluating primary and secondary preventive efforts. Different nomenclatures have been proposed for gastric precancerous lesions in eastern countries and in Japan. This article presents a classification of gastric precancerous lesions resulting from an international consensus conference involving pathologists of different countries. Five main diagnostic categories are identified. To allow comparisons with the nomenclature proposed by the Japanese Research Society for Gastric Cancer, each category was also assigned a numeric identification: 1 = normal, 2 = indefinite for dysplasia, 3 = noninvasive neoplasia, 4 = suspicious for invasive cancer, and 5 = cancer. The interobserver reproducibility of the histologic classification was tested in a series of 46 cases. By collapsing benign alterations (categories 1+2) versus noninvasive neoplasia (category 3) versus suspicious for invasive cancer and fully appearing carcinomatous lesions (categories 4+5), the general agreement value was 77.7%, whereas kappa coefficient was 0.63. By examining gastric precancerous lesions from diverse populations, the authors agreed that the gastric precancerous process is universal and the differences in nomenclatures are merely semantics. The international Padova classification of the gastric precancerous lesions is submitted to the attention of the international scientific community, which is invited to test and to improve on it.

The importance of HER2 status in breast cancer management has focused attention on the ability of clinical assays to correctly assign HER2 amplification status. There is no consensus as to the best method for assessing HER2 status. Disadvantages of fluorescence in situ hybridization (FISH) testing include longer time required for staining and scoring slides, requirements for specialized training and fluorescence microscopy, and loss of the signal due to quenching of the fluorescent dye. Silver-enhanced in situ hybridization (SISH) is a rapid fully automated assay providing permanently stained slides that are interpreted by conventional bright field microscopy which enables pathologists to evaluate slides within the context of tissue morphology. This study evaluates the concordance between SISH and FISH assays in determining the status of HER2 gene amplification in a cohort of 298 primary invasive breast carcinomas. Furthermore, we assessed in detail the variables contributing to interobserver interpretive reproducibility of HER2 SISH among 10 pathologists. HER2 was quantified using the ratio of HER2 to CHR17 signals using the conventional historical interpretation scale and also by the American Society of Clinical Oncology/College of American Pathologists reporting scheme. For SISH status determined by consensus among 10 pathologists, overall concordance between SISH and FISH was identified in 288 of 298 cases (96.6%) using the conventional Food and Drug Administration approved criteria. Overall agreement was observed in 282 of 285 cases (98.9%) using the American Society of Clinical Oncology/College of American Pathologists result reporting scheme (with equivocal cases removed). In conclusion, SISH represents a novel approach for the determination of HER2 status in breast cancer. The overall concordance between SISH and FISH is excellent, and the interpretation of SISH results by pathologists is most reproducible using the HER2/CHR17 ratio.

Although the categorization of proliferative breast lesions provides valuable information regarding subsequent risk of breast cancer, the ability of pathologists to classify such lesions in a reproducible fashion has not been adequately evaluated. To assess further interobserver reproducibility in the categorization of proliferative breast lesions, six pathologists each reviewed 24 proliferative ductal lesions and classified them as either usual hyperplasia (H), atypical hyperplasia (AH), or carcinoma in situ (CIS). Before evaluation of the study slides, all the participants were instructed to use the diagnostic criteria of Page and co-workers and were provided with both a written summary of these criteria and a set of teaching slides with representative examples of each type of lesion. Complete agreement among all six pathologists was seen in 14 cases (58%); five or more agreed in 17 cases (71%); and four or more arrived at the same diagnosis in 22 cases (92%). No pathologist consistently rendered more "benign" or "malignant" diagnoses than any other. After assigning numerical values for each diagnostic category (H = 1, AH = 2, CIS = 3), the scores for the group of 24 cases did not differ significantly by pathologist (p = 0.68; average score range, 1.7-2.0). Our results indicate that with the use of standardized criteria, interobserver concordance in the diagnosis of proliferative ductal breast lesions can be obtained in the majority of cases.

We sought to assess the interobserver variation of the new International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification of lupus nephritis when compared with the previous World Health Organization classification, when used by pathologists throughout the UK. We also sought differences in how the 2 classifications were applied to a single set of biopsies. Twenty unselected renal biopsies showing lupus nephritis were circulated to pathologists in the UK National Renal Pathology External Quality Assessment Scheme, before the ISN/RPS scheme was published, with a request to apply the World Health Organization classification. The same slides were recirculated approximately 1 year later with a request to apply the ISN/RPS classification. A significant improvement in interobserver reproducibility was demonstrated by the new classification (kappa 0.53 vs. 0.44, P = 0.002). The reproducibility of the assessment of disease activity and chronicity remains suboptimal (kappa = 0.33). The new classification tends to produce more diagnoses of Class IV lupus nephritis, with fewer diagnoses of Classes III and V. The improvement in interobserver reproducibility indicates that an important aim of the new classification has been achieved. Further work is needed to determine whether the increase in diagnosis of Class IV nephritis represents an improvement in biopsy interpretation or a divergence from the previous classification, as the latter could undermine attempts to relate results from the new system to treatment strategies based on clinical trials which used the old.