Results from the UNITED study: a multicenter study validating the prognostic effect of the tumor-stroma ratio in colon cancer.

BACKGROUND: The TNM (tumor-node-metastasis) Evaluation Committee of Union for International Cancer Control (UICC) and College of American Pathologists (CAP) recommended to prospectively validate the cost-effective and robust tumor-stroma ratio (TSR) as an independent prognostic parameter, since high intratumor stromal percentages have previously predicted poor patient-related outcomes. PATIENTS AND METHODS: The 'Uniform Noting for International application of Tumor-stroma ratio as Easy Diagnostic tool' (UNITED) study enrolled patients in 27 participating centers in 12 countries worldwide. The TSR, categorized as stroma-high (>50%) or stroma-low (≤50%), was scored through standardized microscopic assessment by certified pathologists, and effect on disease-free survival (DFS) was evaluated with 3-year median follow-up. Secondary endpoints were benefit assessment of adjuvant chemotherapy (ACT) and overall survival (OS). RESULTS: A total of 1537 patients were included, with 1388 eligible stage II/III patients curatively operated between 2015 and 2021. DFS was significantly shorter in stroma-high (n = 428) than in stroma-low patients (n = 960) (3-year rates 70% versus 83%; P < 0.001). In multivariate analysis, TSR remained an independent prognosticator for DFS (P < 0.001, hazard ratio 1.49, 95% confidence interval 1.17-1.90). As secondary outcome, DFS was also worse in stage II and III stroma-high patients despite adjuvant treatment (3-year rates stage II 73% versus 92% and stage III 66% versus 80%; P = 0.008 and P = 0.011, respectively). In stage II patients not receiving ACT (n = 322), the TSR outperformed the American Society of Clinical Oncology (ASCO) criteria in identifying patients at risk of events (event rate 21% versus 9%), with a higher discriminatory 3-year DFS rate (stroma-high 80% versus ASCO high risk 91%). A trend toward worse 5-year OS in stroma-high was noticeable (74% versus 83% stroma-low; P = 0.102). CONCLUSION: The multicenter UNITED study unequivocally validates the TSR as an independent prognosticator, confirming worse outcomes in stroma-high patients. The TSR improved current selection criteria for patients at risk of events, and stroma-high patients potentially experienced chemotherapy resistance. TSR implementation in pathology diagnostics and international guidelines is highly recommended as aid in personalized treatment.

Accurate staging of non-metastatic colon cancer with CT: the importance of training and practice for experienced radiologists and analysis of incorrectly staged cases.

PURPOSE: To investigate whether locoregional staging of colon cancer by experienced radiologists can be improved by training and feedback to minimize the risk of over-staging into the context of patient selection for neoadjuvant therapy and to identify potential pitfalls of CT staging by characterizing pathologic traits of tumors that remain challenging for radiologists. METHODS: Forty-five cases of stage I-III colon cancer were included in this retrospective study. Five experienced radiologists evaluated the CTs; 5 baseline scans followed by 4 sequential batches of 10 scans. All radiologists were trained after baseline scoring and 2 radiologists received feedback. The learning curve, diagnostic performance, reader confidence, and reading time were evaluated with pathologic staging as reference. Pathology reports and H&E slides of challenging cases were reviewed to identify potential pitfalls. RESULTS: Diagnostic performance in distinguishing T1-2 vs. T3-4 improved significantly after training and with increasing number of reviewed cases. Inaccurate staging was more frequently related to under-staging rather than over-staging. Risk of over-staging was minimized to 7% in batch 3-4. N-staging remained unreliable with an overall accuracy of 61%. Pathologic review identified two tumor characteristics causing under-staging for T-stage in 5/7 cases: (1) very limited invasive part beyond the muscularis propria and (2) mucinous composition of the invading part. CONCLUSION: The high accuracy and specificity of T-staging reached in our study indicate that sufficient training and practice of experienced radiologists can ensure high validity for CT staging in colon cancer to safely use neoadjuvant therapy without significant risk of over-treatment, while N-staging remained unreliable.

Daily practice in guideline adherence to adjuvant chemotherapy in stage III colon cancer and predictors of outcome.

INTRODUCTION: Although guidelines recommend adjuvant chemotherapy for stage III colon cancer patients, many patients do not receive adjuvant chemotherapy. The aim of this study was to identify reasons for guideline non-adherence and assess the effect on patient outcomes in a multicenter cohort of stage III colon cancer patients who received surgery plus adjuvant chemotherapy or surgery alone. METHODS: Patients who underwent surgery between 2007 and 2017 were included. Reasons for non-adherence were determined. Propensity score analyses with inverse probability weighting were performed to adjust for confounding factors. Cox proportional hazards regression and risk stratified analyses were performed to assess the association of guideline adherence and other potential predictors with recurrence free survival (RFS). RESULTS: Data of 575 patients were included of whom 61% received adjuvant chemotherapy. In 87 of 222 patients (39%) who did not receive adjuvant chemotherapy, no reason was documented. Only age was predictive for receiving chemotherapy. Patients who received adjuvant chemotherapy had longer RFS (HR 0.42, 95%CI 0.29-0.62, p < 0.001). High T- and N-stage were associated with poorer RFS HR 2.0 (95%CI 1.58-2.71, p < 0.001) and HR 2.19 (95%CI 1.60-2.99, p < 0.001) respectively. Risk groups were identified with distinct prognosis and treatment effect and a nomogram is presented to visualize individualized RFS differences. CONCLUSION: This study shows considerable variation in guideline adherence to adjuvant chemotherapy and poor documentation on reasons for non-adherence. Optimizing adherence and gaining insight in reasons for non-adherence is advocated as this can lead to significant RFS benefit, especially in patients with high T-and N-stage tumors.

Improving clinical management of colon cancer through CONNECTION, a nation-wide colon cancer registry and stratification effort (CONNECTION II trial): rationale and protocol of a single arm intervention study.

BACKGROUND: It is estimated that around 15-30% of patients with early stage colon cancer benefit from adjuvant chemotherapy. We are currently not capable of upfront selection of patients who benefit from chemotherapy, which indicates the need for additional predictive markers for response to chemotherapy. It has been shown that the consensus molecular subtypes (CMSs), defined by RNA-profiling, have prognostic and/or predictive value. Due to postoperative timing of chemotherapy in current guidelines, tumor response to chemotherapy per CMS is not known, which makes the differentiation between the prognostic and predictive value impossible. Therefore, we propose to assess the tumor response per CMS in the neoadjuvant chemotherapy setting. This will provide us with clear data on the predictive value for chemotherapy response of the CMSs. METHODS: In this prospective, single arm, multicenter intervention study, 262 patients with resectable microsatellite stable cT3-4NxM0 colon cancer will be treated with two courses of neoadjuvant and two courses of adjuvant capecitabine and oxaliplatin. The primary endpoint is the pathological tumor response to neoadjuvant chemotherapy per CMS. Secondary endpoints are radiological tumor response, the prognostic value of these responses for recurrence free survival and overall survival and the differences in CMS classification of the same tumor before and after neoadjuvant chemotherapy. The study is scheduled to be performed in 8-10 Dutch hospitals. The first patient was included in February 2020. DISCUSSION: Patient selection for adjuvant chemotherapy in early stage colon cancer is far from optimal. The CMS classification is a promising new biomarker, but a solid chemotherapy response assessment per subtype is lacking. In this study we will investigate whether CMS classification can be of added value in clinical decision making by analyzing the predictive value for chemotherapy response. This study can provide the results necessary to proceed to future studies in which (neo) adjuvant chemotherapy may be withhold in patients with a specific CMS subtype, who show no benefit from chemotherapy and for whom possible new treatments can be investigated. TRIAL REGISTRATION: This study has been registered in the Netherlands Trial Register (NL8177) at 11-26-2019, https://www.trialregister.nl/trial/8177 . The study has been approved by the medical ethics committee Utrecht (MEC18/712).

STAT3 as a predictive biomarker in head and neck cancer: A validation study.

Locally advanced head and neck squamous cell carcinoma (LAHNSCC) treatment consists of radiotherapy (RT) alone or cisplatin-based concomitant chemoradiotherapy (CCRT). CCRT is accompanied by substantially more toxicity than RT alone. A previous retrospective cohort study found that LAHNSCC patients with tumors negative for nuclear expression of the signal transducer and activator of transcription 3 (STAT3) protein might not benefit from the addition of cisplatin to radiotherapy (RT) treatment. We set out to validate these results in a new cohort. We found that in patients with both STAT3 positive and negative tumors, disease-free survival (DFS) and overall survival (OS) did not differ significantly between treatment with cisplatin-based concomitant chemoradiotherapy (CCRT) and radiotherapy alone. Therefore, our validation study does not confirm that STAT3 is a potential biomarker to predict the effectiveness of the addition of cisplatin to RT in LAHNSCC patients.

Memento for interprofessional learning.

The vast increase of technical, diagnostic, and treatment possibilities and deepened understanding of molecular biology has revolutionized diagnosis and treatment of cancer and thus has great impact on pathology. Different professionals are responsible for proper evaluation of the results and their translating into an accurate diagnosis and appropriate treatment. Next to expertise, a close interaction between clinical molecular biologists, pathologists, and oncologists is required; it is crucial that these professionals speak "the same language." Key to this is communication skills and creating possibilities for collaboration in a meaningful context. Here, we present an interprofessional, educational workshop model and we describe the parameters that contribute to effective learning by specialists.

Scoring the tumor-stroma ratio in colon cancer: procedure and recommendations.

The tumor-stroma ratio (TSR) has been reported as a strong, independent prognostic parameter in colon cancer as well as in other epithelial cancer types, and may be implemented to routine pathology diagnostics. The TSR is an easy technique, based on routine hematoxylin and eosin stained histological sections, estimating the amount of stroma present in the primary tumor. It links tumors with high stromal content to poor prognosis. The analysis time is less than 2 min with a low inter-observer variation. Scoring of the TSR has been validated in a number of independent international studies. In this manuscript, we provide a detailed technical description of estimating the TSR in colon cancer, including examples, pitfalls, and recommendations.

RAS testing for colorectal cancer patients is reliable in European laboratories that pass external quality assessment.

Wild-type status of KRAS and the NRAS gene (exon 2, 3, and 4) in the tumor should be determined before treatment of metastatic colorectal cancer (mCRC) patients with EGFR-targeting agents. There is a large variation in test methods to determine RAS status, and more sensitive detection methods were recently introduced. Data from quality assessment programs indicate substantial error rates. This study assessed the completeness and correctness of RAS testing in European laboratories that successfully passed external quality assessment (EQA). Participants were requested to send material of their most recent ten patients with mCRC who had been tested for RAS status. Isolated DNA, a hematoxylin and eosin stained tissue slide with a marked area for macrodissection and accompanying patient reports were requested. Samples were reevaluated in a reference laboratory by using a next-generation sequencing approach. In total, 31 laboratories sent in the requested material (n = 309). Despite regulations for anti-EGFR therapy, one institute did not perform full RAS testing. Reanalysis was possible for 274 samples with sufficient DNA available. In the hotspot codons of KRAS and NRAS, seven discordant results were obtained in total, five of them leading to a different prediction of anti-EGFR therapy efficacy (2%; n = 274). Results show that oncologists can rely on the quality of laboratories with good performance in EQA. Oncologists need to be aware that the testing laboratory participates successfully in EQA programs. Some EQA providers list the good performing laboratories on their website.

Concordant bone marrow involvement of diffuse large B-cell lymphoma represents a distinct clinical and biological entity in the era of immunotherapy.

In diffuse large B-cell lymphoma (DLBCL), the clinical and biological significance of concordant and discordant bone marrow (BM) involvement have not been well investigated. We evaluated 712 de novo DLBCL patients with front-line rituximab-containing treatment, including 263 patients with positive and 449 with negative BM status. Compared with negative BM disease, concordant BM adversely impacted overall and progression-free survival, independent of the International Prognostic Index (IPI) and cell-of-origin classification. Once BM is concordantly involved, poor prognosis was not associated with the extent of BM involvement. Conversely, patients with discordant BM showed favorable overall survival similar to stage I-II DLBCL. A BM-adjusted IPI, using three parameters: concordant BM involvement, age >60 years, and performance status >1, improves the risk stratification for DLBCL with positive BM. Intensive immunochemotherapy seemingly rendered survival benefit for patients with concordant BM, as did rituximab maintenance for the discordant BM group. Frequently revealing adverse clinical and molecular characteristics, patients with concordant BM demonstrated gene expression signatures relevant to tumor cell proliferation, migration and immune escape. In conclusion, clinical and biological heterogeneity is seen in DLBCL with positive BM but concordant BM involvement represents a distinct subset with unfavorable gene signatures, high-risk clinicopathologic features and poor prognosis.

Loss of PRDM1/BLIMP-1 function contributes to poor prognosis of activated B-cell-like diffuse large B-cell lymphoma.

PRDM1/BLIMP-1, a master regulator of plasma-cell differentiation, is frequently inactivated in activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL) patients. Little is known about its genetic aberrations and relevant clinical implications. A large series of patients with de novo DLBCL was effectively evaluated for PRDM1/BLIMP-1 deletion, mutation, and protein expression. BLIMP-1 expression was frequently associated with the ABC phenotype and plasmablastic morphologic subtype of DLBCL, yet 63% of the ABC-DLBCL patients were negative for BLIMP-1 protein expression. In these patients, loss of BLIMP-1 was associated with Myc overexpression and decreased expression of p53 pathway molecules. In addition, homozygous PRDM1 deletions and PRDM1 mutations within exons 1 and 2, which encode for domains crucial for transcriptional repression, were found to show a poor prognostic impact in patients with ABC-DLBCL but not in those with germinal center B-cell-like DLBCL (GCB-DLBCL). Gene expression profiling revealed that loss of PRDM1/BLIMP-1 expression correlated with a decreased plasma-cell differentiation signature and upregulation of genes involved in B-cell receptor signaling and tumor-cell proliferation. In conclusion, these results provide novel clinical and biological insight into the tumor-suppressive role of PRDM1/BLIMP-1 in ABC-DLBCL patients and suggest that loss of PRDM1/BLIMP-1 function contributes to the overall poor prognosis of ABC-DLBCL patients.

How we do: optimizing bone marrow biopsy logistics for sign-out within 2 days.

Since the introduction of fast diagnostic tracks in many areas of oncology, the traditional processing of bone marrow biopsies (BMB), requiring either resin embedding or lengthy fixation and decalcification, is due to an upgrade. Thanks to a growing number of new commercially available tissue processors, microwave-enhanced processing is becoming a standard tool in the pathology laboratory, allowing rapid fixation and decalcification of BMB with preserved morphology and antigens. In this short report, we describe the use of a commercially available EDTA-based decalcification fluid (USEDECALC, Medite, Orlando, USA) in combination with the LOGOS J (Milestone, Bergamo, Italy), a closed microwave-enhanced tissue processor, for overnight fixation, decalcification, and paraffin impregnation of the BMB. This allows next-day reporting without impaired morphology or immunohistochemistry, and even improved DNA quality of the BMB.

ESMO consensus guidelines for the management of patients with metastatic colorectal cancer.

Colorectal cancer (CRC) is one of the most common malignancies in Western countries. Over the last 20 years, and the last decade in particular, the clinical outcome for patients with metastatic CRC (mCRC) has improved greatly due not only to an increase in the number of patients being referred for and undergoing surgical resection of their localised metastatic disease but also to a more strategic approach to the delivery of systemic therapy and an expansion in the use of ablative techniques. This reflects the increase in the number of patients that are being managed within a multidisciplinary team environment and specialist cancer centres, and the emergence over the same time period not only of improved imaging techniques but also prognostic and predictive molecular markers. Treatment decisions for patients with mCRC must be evidence-based. Thus, these ESMO consensus guidelines have been developed based on the current available evidence to provide a series of evidence-based recommendations to assist in the treatment and management of patients with mCRC in this rapidly evolving treatment setting.

A 20-year population-based study on the epidemiology, clinical features, treatment, and outcome of nodular lymphocyte predominant Hodgkin lymphoma.

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is a subtype of Hodgkin lymphoma characterized by a unique clinical and histological presentation. Because of the rare nature of this disease, few large-scale studies are available. We conducted a cohort study in which patients were identified in the Netherlands Cancer Registry in the Southeast of the Netherlands between 1990 and 2010. Of these patients, we collected all clinical characteristics and re-reviewed pathologic material to confirm NLPHL diagnosis. Seventy-three histologically confirmed cases of NLPHL were analyzed with a median follow-up of 65 months (range 4-257 months). Median age at diagnosis was 43 years (range 1-87); 84.9 % of the patients were male; B symptoms were present in 5.5 %; and stage I/II disease was most common (75.4 %). Patients were primarily treated with radiotherapy (50.7 %), chemotherapy (26 %), combined modality (radiotherapy and chemotherapy) (11 %), or surgical excision with careful watch-and-wait (12.3 %). Relapses occurred in seven patients (9.6 %) after a median of 26 months (21-74 months). Six patients (8.2 %) developed histologic transformation to large cell lymphoma. Five patients (6.8 %) died during follow-up due to progression of NLPHL (n = 1), histologic transformation (n = 2) and intercurrent deaths (n = 2). The estimated 10-year overall survival was 94.0 % and the 10-year progression-free survival 75.8 %. Our study confirms the distinct characteristics of NLPHL with a relatively good long-term prognosis. It may be possible to reduce treatment intensity in early stage NLPHL without affecting long-term outcome.

Prevalence of RAS mutations and individual variation patterns among patients with metastatic colorectal cancer: A pooled analysis of randomised controlled trials.

BACKGROUND: The use of epidermal growth factor receptor inhibitors to treat metastatic colorectal cancer (mCRC) patients requires prior confirmation of tumour wild type (WT) RAS mutation status (exons 2/3/4 for KRAS or NRAS). This retrospective pooled analysis aims to robustly estimate RAS mutation prevalence and individual variation patterns in mCRC patients. METHOD: Individual patient data from five randomised, controlled panitumumab studies (three phase III, one phase II and one phase Ib/II) were pooled for this analysis. The phase III studies included mCRC patients independent of RAS mutation status; the phase II and Ib/II studies included mCRC patients with confirmed WT KRAS exon 2 status. Four studies conducted RAS testing using Sanger sequencing; one study used a combination of next-generation sequencing and Sanger sequencing. In order to assign overall RAS status, the mutation status of all exons 2/3/4 KRAS or NRAS was required to be known. RESULTS: Data from 3196 mCRC patients from 36 countries were included in the analysis. The overall unadjusted RAS mutation prevalence in mCRC patients was 55.9% (95% confidence interval (CI): [53.9-57.9%]), with the following distribution observed: KRAS exon 2 (prevalence 42.6% [40.7-44.5%]); KRAS exon 3 (3.8% [2.9-4.9%]); KRAS exon 4 (6.2% [5.0-7.6%]); NRAS exon 2 (2.9% [2.1-3.9%]); NRAS exon 3 (4.2% [3.2-5.4%]); NRAS exon 4 (0.3% [0.1-0.7%]). Differences in RAS mutation prevalence estimates were observed by study (p=0.001), gender (p=0.030), and by country (p=0.028). CONCLUSIONS: This analysis provides robust estimates of overall RAS mutation prevalence and individual variation patterns in mCRC patients.

FOLFOX4 plus cetuximab treatment and RAS mutations in colorectal cancer.

BACKGROUND: The OPUS study demonstrated that addition of cetuximab to 5-fluorouracil, folinic acid and oxaliplatin (FOLFOX4) significantly improved objective response and progression-free survival (PFS) in the first-line treatment of patients with KRAS exon 2 wild-type metastatic colorectal cancer (mCRC). In patients with KRAS exon 2 mutations, a detrimental effect was seen upon addition of cetuximab to FOLFOX4. The current study reports outcomes in subgroups defined by extended RAS testing. PATIENTS AND METHODS: Samples from OPUS study KRAS exon 2 wild-type tumours were reanalysed for other RAS mutations in four additional KRAS codons (exons 3-4) and six NRAS codons (exons 2-4) using BEAMing. A cutoff of ⩾5% mutant/wild-type sequences was selected to define RAS status; we also report an analysis using a cutoff based on the technical lower limit for mutation identification (0.1%). RESULTS: Other RAS mutations were detected in 31/118 (26%) evaluable patients. In the extended analysis of RAS wild-type tumours (n=87), objective response was significantly improved by addition of cetuximab to FOLFOX4 (58% versus 29%; odds ratio 3.33 [95% confidence interval 1.36-8.17]; P=0.0084); although limited by population size, there also appeared to be trends favouring the cetuximab arm in terms of PFS and overall survival in the RAS wild-type group compared with the RAS evaluable group. There was no evidence that patients with other RAS mutations benefited from cetuximab, but small numbers precluded precise estimations of treatment effects. In the combined population of patients with any RAS mutation (KRAS exon 2 or other RAS), a clear detrimental effect was associated with addition of cetuximab to FOLFOX4. CONCLUSION: Patients with RAS-mutant mCRC, as defined by mutations in KRAS and NRAS exons 2-4, derive no benefit and may be harmed by the addition of cetuximab to FOLFOX4. Restricting cetuximab administration to patients with RAS wild-type tumours will further tailor therapy to maximise benefit.

Trends in quality of non-Hodgkin's lymphoma care: is it getting better?

This study outlines trends in quality of delivered non-Hodgkin's lymphoma (NHL) care in the Netherlands between 2007 and 2011 and to what extend this was influenced by the national Visible Care program, which aimed at increasing transparency by providing insight into the quality of healthcare. We analyzed data collected from medical records in two observational studies, combined into 20 validated quality indicators (QIs) of which 6 were included in the national program. A random sample of 771 patients, diagnosed with NHL in 26 Dutch hospitals, was examined. Multilevel regression analyses were used to assess differences in quality of NHL care and to provide insight into the effect of the national program. We reported improved adherence to only 3 out of 6 QIs involved in the national program and none of the other 14 validated QIs. Improvement was shown for performance of all recommended staging techniques (from 26 to 43 %), assessment of International Prognostic Index (from 21 to 43 %), and multidisciplinary discussion of patients (from 23 to 41 %). We found limited improvement in quality of NHL care between 2007 and 2011; improvement potential (<80 % adherence) was still present for 13 QIs. The national program seems to have a small positive effect, but has not influenced all 20 indicators which represent the most important, measurable parts in quality of NHL care. These results illustrate the need for tailored implementation and quality improvement initiatives.

No change in lymph node positivity rate despite increased lymph node yield and improved survival in colon cancer.

AIM: To analyse trends over time in the number of lymph nodes evaluated and in the proportion of node positivity and to investigate the impact on survival for patients with colon cancer. PATIENTS AND METHODS: 8616 patients resected for M0 colon cancer diagnosed in the southern Netherlands between 2000 and 2011 were included in this study. Trends in nodal evaluation and node positivity were analysed. Multivariable logistic regressions were used to assess the influence of period of diagnosis on adequate nodal evaluation (P12 lymph nodes) and no depositivity after adjusting for patient and tumour characteristics. Crude 5-year relative survival was used as an estimate for disease-specific survival. RESULTS: Overall, the proportion adequate nodal evaluation increased from 13% in 2000­2002 to 59% in 2009­2011 (p < 0.0001), whereas the proportion node positivity remained similar across study periods (approximately 35%). Patients diagnosed in later periods were more likely to have received adequate nodal yield (adjusted Odds ratio (OR) 2009­2011 versus 2000­2002 9.8, 95% Confidence interval (CI) 8.3­11.6). However, the adjusted odds of having node positive disease did not differ between periods of diagnosis. Relative excess risk of dying was independently correlated with the number of lymph nodes evaluated (1­8 LNs versus P12 LNs, N0: 2.2, 95% CI 1.7­2.9; N+: 1.7, 95% CI 1.4­2.0) and period of diagnosis (2009­2011 versus 2000­2002, N+ only: 0.8, 95% CI 0.6­1.0). CONCLUSION: The reason for improved survival with increased nodal yield is different from simple understaging as the proportion of lymph node positivity remained constant.

HNF4A immunohistochemistry facilitates distinction between primary and metastatic breast and gastric carcinoma.

The distinction between primary gastric adenocarcinoma and gastric metastatic breast carcinoma can be difficult. Expression of hepatocyte nuclear factor 4A (HNF4A) has been described as being specific to distinguish between neoplastic gastric and breast epithelial cells. The aim of this study was to validate the use of HNF4A with immunohistochemistry in discriminating gastric from breast carcinomas. Immunohistochemical expressions of HNF4A, estrogen receptor (ER), progesterone receptor (PR), and BRST-2 were determined in primary sporadic gastric adenocarcinomas (n = 107) and breast carcinomas (n = 105). The same markers and clinicopathological features were studied in 1 patient with breast metastasis of gastric cancer, 6 patients with gastric metastases of breast cancer, and 13 patients with both primary gastric and breast carcinomas. HNF4A expression was seen in 106 of 107 primary gastric adenocarcinomas and was absent in all 105 primary breast carcinomas (sensitivity 99 %, specificity 100 %). ER, PR, and BRST-2 were 100 % specific for breast carcinomas with sensitivities of 77, 58, and 38 %, respectively. The metastasis of gastric carcinoma to the breast showed strong expression of HNF4A. None of the metastases of breast carcinomas to the stomach showed expression of HNF4A. Tissues of patients with two primary carcinomas showed strong expression of HNF4A in all gastric carcinomas and no expression in breast carcinomas. Our results indicate that HNF4A is a very good marker to discriminate between primary and metastatic gastric and breast carcinomas.