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Notes: Aims: Accurate tumour classification is critical for meaningful epidemiological studies in the assessment of cancer incidence rates and trends. Differentiating primary gastric carcinoma from oesophageal carcinoma can be difficult, especially when tumours are large and involve both the oesophagus and stomach. Furthermore, adenocarcinomas of both organs typically are of intestinal histological type and arise in a background of intestinal metaplasia. Consequently, histological markers that reliably distinguish Barrett's-related oesophageal adenocarcinoma from gastric adenocarcinoma would be useful. Cytokeratins (CK)7 and 20 are cytoplasmic structural proteins with restricted expression that help to determine the origin of many epithelial tumours including those of the gastrointestinal tract. The aim of this study was to determine the utility of co-ordinate CK7 and 20 expression in the distinction of Barrett's-related oesophageal adenocarcinoma from gastric adenocarcinoma arising in a background of intestinal metaplasia.Methods and results: CK7 and 20 immunostaining was performed on randomly selected surgical resection specimens from patients with Barrett's-related oesophageal adenocarcinoma (n = 30) and intestinal type gastric adenocarcinoma (n = 14) arising in a background of intestinal metaplasia. A CK7+ CK20- immunophenotype was demonstrated in 27 of 30 (90%) patients with Barrett's-related oesophageal adenocarcinoma and only three of 14 (21%) gastric adenocarcinomas. The sensitivity, specificity and positive predictive value of a CK7+/20– immunophenotype for a diagnosis of Barrett's-related oesophageal adenocarcinoma was 90%, 79%, and 90%, respectively.Conclusions: A CK7+/20– tumour immunophenotype is associated with Barrett's-related oesophageal adenocarcinoma and may be useful in accurate tumour classification, thus facilitating improving epidemiological evaluation of tumours at the oesophagogastric junction.

Notes: Aims:  In some cases distinction between chromophobe renal cell carcinoma (CRCC), oncocytoma and clear cell (conventional) renal cell carcinoma (eosinophilic variant) using routine light microscopy remains problematic. The present study investigates the level of agreement in the diagnosis of CRCC, as well as the histological features most frequently used for this diagnosis by two pathologists with a special interest in renal neoplasia. The sensitivity and specificity of immunohistochemical markers in cases with overlapping histological features in the diagnosis of CRCC were also studied. Electron microscopy was performed, as a diagnostic gold standard, on all of the cases.Methods and results:  Thirty-two renal tumours with predominantly eosinophilic cytoplasm were reviewed in a blinded fashion by two pathologists. The diagnosis and morphological features used to render each diagnosis were tabulated. Validation of the utility of keratin 7 and 20, epithelial membrane antigen (EMA), vimentin, CD10, parvalbumin, RCC antigen, antimitochondrial antibody and Hale's colloidal iron was performed by the construction of a tissue microarray (TMA) master block. Based on histological criteria alone, overall agreement on the diagnosis of these tumours was reached in 69% of the cases, while there was total disagreement in 12%. In 59% of the cases, total agreement was reached in classifying the case as a CRCC based on histology alone. Kappa statistics for interobserver variability were calculated as only slight agreement (κ = 0.3). The histological features most frequently associated with a diagnosis of CRCC were accentuated cell borders (87%) and a combination of hyperchromatic wrinkled nuclei (79%) and perinuclear halos (74%). The most sensitive and specific marker for CRCC was parvalbumin (sensitivity 0.91; specificity 1.0). The immunohistochemical profile of EMA+/ vimentin– was useful but had low specificity (sensitivity 0.75; specificity 0.4). CD10 had the highest sensitivity (1.0) but worst specificity (0.25) for CRCC. Keratin 7 had high sensitivity (0.83) but fairly low specificity (0.37) for CRCC. Hale's colloidal iron and the RCC antigen marker were not contributory. Finally, the antimitochondrial antibody was found to be fairly sensitive (0.83) for excluding CRCC.Conclusions:  A small but significant proportion of renal tumours with cells having eosinophilic cytoplasm cannot be classified, even by experienced pathologists, based on histology alone. In these cases it is imperative to use markers with known sensitivity and specificity for the diagnosis of CRCC.

Notes: Aims:  Keratin 903 (also known as anti-cytokeratin antibody 34βE12) is widely used to differentiate benign glands from malignant glands in prostate needle biopsies. However, it is subject to considerable staining heterogeneity. We sought to evaluate the use of cytokeratin 5/6 (CK5/6) as an effective alternative to K903 in the evaluation of prostate needle biopsies in clinical practice.Methods and results:  Thirty Hollandes-fixed prostate needle biopsies were randomly selected over a period of 2 months from the surgical specimens accessioned over that period of time. Twelve cases had diagnosed prostatic adenocarcinoma (Gleason scores 3 + 3, 3 + 4 and 4 + 4) and the remaining cases (n = 18) were negative for carcinoma. Four sequential sections were stained with H&E (×2), K903, and CK5/6. Care was taken to preserve tissue so that matching glands were evaluated on all four sections. All cases were run routinely over a period of 3 weeks on a daily basis with matching positive controls. All slides were evaluated in a blinded fashion independently by two pathologists using a semiquantitative analysis of staining: 〈25%, 25–50%, 50–75%, 〉75% and 〉95% of benign glands (verified on H&E). Cases that showed no staining were repeated to ensure no false negatives. Both observers agreed with respect to percentage of staining in 96% of the cases. Twenty-nine of 30 cases (97%) showed staining in 〉95% of benign glands with CK5/6. In contrast, K903 staining was seen in 〈50% of benign glands in five of 30 (17%), 50–75% in nine of 30 (30%), and 〉75% in 10 of 30 (33%), with only two cases (7%) showing 〉95% staining for K903. In four cases (13%) the K903 failed to stain any tissue even after repeat staining. K903 was conspicuously negative in atrophic glands in three of 30 cases (10%). Neither K903 nor CK5/6 stained malignant glands. Using a cut-off of 〉75% staining in benign glands the sensitivity of CK5/6 and K903 was 97% and 40%, respectively.Conclusions:  CK5/6 has superior sensitivity and reliability compared with that of K903 when evaluating routine prostate needle biopsies, including improved staining of atrophic prostatic glands. While K903 is traditionally used to differentiate benign glands from malignant glands, these results support the use of CK5/6 as an effective and reliable substitute for K903 in routine clinical practice.