Driver mutations in GNAQ and GNA11 genes as potential targets for precision immunotherapy in uveal melanoma patients.

Uveal melanoma (UM) is the most common ocular malignancy in adults. Nearly 95% of UM patients carry the mutually exclusive mutations in the homologous genes GNAQ (amino acid change Q209L/Q209P) and GNA11 (aminoacid change Q209L). UM is located in an immunosuppressed organ and does not suffer immunoediting. Therefore, we hypothesize that driver mutations in GNAQ/11 genes could be recognized by the immune system. Genomic and transcriptomic data from primary uveal tumors were collected from the TCGA-UM dataset (n = 80) and used to assess the immunogenic potential for GNAQ/GNA11 Q209L/Q209P mutations using a variety of tools and HLA type information. All prediction tools showed stronger GNAQ/11 Q209L binding to HLA than GNAQ/11 Q209P. The immunogenicity analysis revealed that Q209L is likely to be presented by more than 73% of individuals in 1000 G databases whereas Q209P is only predicted to be presented in 24% of individuals. GNAQ/11 Q209L showed a higher likelihood to be presented by HLA-I molecules than almost all driver mutations analyzed. Finally, samples carrying Q209L had a higher immune-reactive phenotype. Regarding cancer risk, seven HLA genotypes with low Q209L affinity show higher frequency in uveal melanoma patients than in the general population. However, no clear association was found between any HLA genotype and survival. Results suggest a high potential immunogenicity of the GNAQ/11 Q209L variant that could allow the generation of novel therapeutic tools to treat UM like neoantigen vaccinations.

Validation of Modaplex POLE mutation assay in endometrial carcinoma.

The TCGA-based molecular classification of endometrial cancer has emerged as an important tool to stratify patients according to prognosis. A simplified scheme has been proposed, by using immunohistochemistry for p53, MSH6, and PMS2 and a molecular test for POLE mutations (NGS or Sanger sequencing, techniques that are not available in many centers worldwide). In this study, we validate a novel method that allows simultaneous analysis of multiple pathogenic POLE mutations. The Modaplex technology integrates polymerase chain reaction and capillary electrophoresis. The design of this study encompassed 4 different steps: (1) a retrospective-pilot phase, with 80 tumors, balancing the four molecular subgroups. (2) A retrospective phase of 25 tumors obtained between 2016 and 2020, and 30 tumors obtained between 2000 and 2015. (3) An inter-laboratory corssavalidation step with 19 cases (belonging to phases 1 and 2). (4) A prospective cohort of 123 tumors, of unknown POLE status, with simultaneous validation by Sanger sequencing. A total of 258 samples were analyzed. In the first and second phases, the test showed positive/negative predictive values of 100%, by correctly identifying POLE mutation status in 79/79 and 55/55 cases. Phase 3 showed 100% of inter-laboratory consistency. Phase 4 showed 16 positive samples out of the 123 prospective cases. Overall, the test has revealed sensitivity and specificity of 100%, identifying a total of 47 POLE-mutated tumors. We have shown that this technique allows faster and easier identification of multiple pathogenic POLE mutations with high robustness and confidence when comparing to other tests such as Sanger sequencing.

Orthotopic murine xenograft model of uveal melanoma with spontaneous liver metastasis.

Uveal melanoma is the most common intraocular malignancy in adults. Despite the effective primary treatment, up to 50% of patients with uveal melanoma will develop metastatic lesions mainly in the liver, which are resistant to conventional chemotherapy and lead to patient's death. To date, no orthotopic murine models of uveal melanoma which can develop spontaneous metastasis are available for preclinical studies. Here, we describe a spontaneous metastatic model of uveal melanoma based on the orthotopic injection of human uveal melanoma cells into the suprachoroidal space of immunodeficient NSG mice. All mice injected with bioluminescent OMM2.5 ( n = 23) or MP41 ( n = 19) cells developed a primary tumor. After eye enucleation, additional bioluminescence signals were detected in the lungs and in the liver. At necropsy, histopathological studies confirmed the presence of lung metastases in 100% of the mice. Liver metastases were assessed in 87 and in 100% of the mice that received OMM2.5 or MP41 cells, respectively. All tumors and metastatic lesions expressed melanoma markers and the signaling molecules insulin-like growth factor type I receptor and myristoylated alanine-rich C-kinase substrate, commonly activated in uveal melanoma. The novelty of this orthotopic mouse xenograft model is the development of spontaneous metastases in the liver from the primary site, reproducing the organoespecificity of metastasis observed in uveal melanoma patients. The faster growth and the high metastatic incidence may be attributed at least in part, to the severe immunodeficiency of NSG mice. This model may be useful for preclinical testing of targeted therapies with potential uveal melanoma antimetastatic activity and to study the mechanisms involved in liver metastasis.

Comparison of the Idylla™ MSI assay with the Promega™ MSI Analysis System and immunohistochemistry on formalin-fixed paraffin-embedded tissue of endometrial carcinoma: results from an international, multicenter study.

Determination of microsatellite instability (MSI) and mismatch repair deficiency (MMRD), respectively, in endometrial carcinomas (ECs) is important for diagnostic and prognostic purposes, identification of Lynch syndrome carriers, and selection of patients for immunotherapy. The Idylla™ MSI assay is fully automated, does not require non-tumoral tissue, and can be performed in about 150 min. Two hundred forty-two formalin-fixed paraffin-embedded (FFPE) EC samples from 7 international centers were tested by the Idylla™ MSI assay and compared to the Promega™ MSI Analysis System and immunohistochemistry (IHC) for MMR proteins. The cases were selected with an enrichment of MSI EC to around 40%. Concordance was 87.5% between the Idylla™ MSI assay and IHC and 88.58% between IHC and Promega™ MSI assay. Concordance between Idylla™ and Promega™ MSI assays was 89.91%. Discordant results occurred more frequently in cases with MSH6 or PMS2 deficiency. Invalid cases occurred with the three techniques (IHC, 7.00%; Promega™ MSI assay, 5.37%; and Idylla™ MSI assay, 2.47%). The concordance rate between Idylla™ MSI assay and the other 2 methods increased to 88.83% for IHC and to 91.22% for the Promega™ MSI assay when the cutoff of instability in the scoring system was moved from 0.5 to 0.3. The Idylla™ MSI assay is a rapid and highly concordant test for MSI in EC. Modification of the Idylla™ scoring system could increase the sensitivity and specificity of the MSI assay for EC analysis.

Efficacy of CDK4/6 inhibitors in preclinical models of malignant pleural mesothelioma.

BACKGROUND: There is no effective therapy for patients with malignant pleural mesothelioma (MPM) who progressed to platinum-based chemotherapy and immunotherapy. METHODS: We aimed to investigate the antitumor activity of CDK4/6 inhibitors using in vitro and in vivo preclinical models of MPM. RESULTS: Based on publicly available transcriptomic data of MPM, patients with CDK4 or CDK6 overexpression had shorter overall survival. Treatment with abemaciclib or palbociclib at 100 nM significantly decreased cell proliferation in all cell models evaluated. Both CDK4/6 inhibitors significantly induced G1 cell cycle arrest, thereby increasing cell senescence and increased the expression of interferon signalling pathway and tumour antigen presentation process in culture models of MPM. In vivo preclinical studies showed that palbociclib significantly reduced tumour growth and prolonged overall survival using distinct xenograft models of MPM implanted in athymic mice. CONCLUSIONS: Treatment of MPM with CDK4/6 inhibitors decreased cell proliferation, mainly by promoting cell cycle arrest at G1 and by induction of cell senescence. Our preclinical studies provide evidence for evaluating CDK4/6 inhibitors in the clinic for the treatment of MPM.

Paired Somatic-Germline Testing of 15 Polyposis and Colorectal Cancer-Predisposing Genes Highlights the Role of APC Mosaicism in de Novo Familial Adenomatous Polyposis.

Familial adenomatous polyposis (FAP) is an autosomal dominant syndrome responsible for 1% of colorectal cancers (CRCs). Up to 90% of classic FAPs are caused by inactivating mutations in APC, and mosaicism has been previously reported in 20% of de novo cases, usually linked to milder phenotypic manifestations. This study aimed to explore the prevalence of mosaicism in 11 unsolved cases of classic FAP and to evaluate the diagnostic yield of somatic testing. Paired samples of colorectal polyps, tumors, and/or mucosa were analyzed using a custom next-generation sequencing panel targeting 15 polyposis and CRC-predisposing genes. Whenever possible, the extension of mosaicism to blood or sperm was also examined. Of 11 patients with classic adenomatous polyposis, a mosaic pathogenic variant in APC was identified in 7 (64%). No other altered genes were identified. In two of seven patients (29%), mosaicism was found restricted to colonic tissues, whereas in five of seven patients (71%), it was extended to the blood. Germline affectation was confirmed in one patient. We report the first analysis at a somatic level of 15 genes associated with CRC susceptibility, which highlights the role of APC mosaicism in classic FAP etiology. The results further reinforce the importance of testing target tissues when blood test results are negative.

Nivolumab Plus Ipilimumab for Treatment-Naïve Metastatic Uveal Melanoma: An Open-Label, Multicenter, Phase II Trial by the Spanish Multidisciplinary Melanoma Group (GEM-1402).

PURPOSE: This study aimed to assess the efficacy of the combination of nivolumab (nivo) plus ipilimumab (ipi) as a first-line therapy with respect to the 12-month overall survival (OS) in patients with metastatic uveal melanoma (MUM) who are not eligible for liver resection. METHODS: This was a single-arm, phase II trial led by the Spanish Multidisciplinary Melanoma Group (GEM) on nivo plus ipi for systemic treatment-naïve patients of age > 18 years, with histologically confirmed MUM, Eastern Cooperative Oncology Group-PS 0/1, and confirmed progressive metastatic disease (M1). Nivo (1 mg/kg once every 3 weeks) and ipi (3 mg/kg once every 3 weeks) were administered during four inductions, followed by nivo (3 mg/kg once every 2 weeks) until progressive disease, toxicity, or withdrawal. The primary end point was 12-month OS. OS, progression-free survival (PFS), and overall response rate were evaluated every 6 weeks using RECIST (v1.1). Safety was also evaluated. Logistic regression and Cox proportional hazard models comprising relevant clinical factors were used to evaluate the potential association with response to treatment and survival. Cytokines were quantified in serum samples for their putative role in immune modulation/angiogenesis and/or earlier evidence of involvement in immunotherapy. RESULTS: A total of 52 patients with a median age of 59 years (range, 26-84 years) were enrolled. Overall, 78.8%, 56%, and 32% of patients had liver M1, extra-liver M1, and elevated lactate dehydrogenase. Stable disease was the most common outcome (51.9%). The primary end point was 12-month OS, which was 51.9% (95% CI, 38.3 to 65.5). The median OS and PFS were 12.7 months and 3.0 months, respectively. PFS was influenced by higher LDH values. CONCLUSIONS: Nivo plus ipi in the first-line setting for MUM showed a modest improvement in OS over historical benchmarks of chemotherapy, with a manageable toxicity profile.

Clonal relationship in multisited mucosa-associated lymphoid tissue lymphomas: a single-centre experience.

Clonal heterogeneity in multisited or recurrent lymphoid neoplasms is a phenomenon that has been increasingly studied in recent years. However, in mucosa-associated lymphoid tissue (MALT) lymphomas it remains largely unexplored. Patients diagnosed at our institution with multisited MALT lymphoma, from January 2009 to October 2018, were studied. Molecular studies were performed for the detection of clonally rearranged immunoglobulin by polymerase chain reaction.In all, 91 patients were included. Of those, 28 had a multisited disease and in 16 clonality studies were done. In eight cases, multifocal involvement was synchronous and in eight metachronous. Patients with non-gastric gastrointestinal tract involvement tended to disseminate within the same tract, without observing other specific dissemination patterns. Four cases (25%) had clonal heterogeneity at the different organs involved. All patients with late relapses (two patients) had different clones. The majority of patients with multisited MALT lymphomas presented with the same clone in the different involved organs, identifying a different clone in those with late relapses. These patients could represent de novo neoplasms, rather than a relapse. This could mean that some individuals might have a genetic predisposition to develop this type of lymphoma and it could also have clinical implications regarding therapeutic decisions.

Clinical performance evaluation of the Idylla™ EGFR Mutation Test on formalin-fixed paraffin-embedded tissue of non-small cell lung cancer.

BACKGROUND: Detection of epidermal growth factor receptor (EGFR) mutations in exons 18-21 is recommended in all patients with advanced Non-small-cell lung carcinoma due to the demonstrated efficiency of the standard therapy with tyrosine kinase inhibitors in EGFR-mutated patients. Therefore, choosing a suitable technique to test EGFR mutational status is crucial to warrant a valid result in a short turnaround time using the lowest possible amount of tissue material. The Idylla™ EGFR Mutation Test is a simple, fast and reliable method designed for the detection of EGFR mutations from formalin-fixed paraffin-embedded samples. The aim of this study was the Clinical Performace Evaluation of the Idylla™ EGFR Mutation Test on the Idylla™ System. METHODS: EGFR mutational status was determined on 132 archived formalin-fixed paraffin-embedded tissue sections with Idylla™ technology. Results were compared with the results previously obtained by routine method in the reference lab (Therascreen® EGFR RGQ PCR v2, Qiagen in Molecular Pathology lab, Hospital Universitario Virgen del Rocío de Sevilla). RESULTS: The overall agreement between results obtained with the Idylla™ EGFR Mutation Test and the Comparator test method was 95.38% (with 1-sided 95% lower limit of 91.7%) showing Positive Diagnostic Agreement of 93.22% and Negative Diagnostic Agreement of 97.18%, with a Limit Of Detection ≤5%. CONCLUSIONS: The Idylla™ EGFR Mutation Test passed its clinical validity performance characteristics for accuracy.

Correction: Lymphangioleiomyomatosis Biomarkers Linked to Lung Metastatic Potential and Cell Stemness.

[This corrects the article DOI: 10.1371/journal.pone.0132546.].

Epigenetic prediction of response to anti-PD-1 treatment in non-small-cell lung cancer: a multicentre, retrospective analysis.

BACKGROUND: Anti-programmed death-1 (PD-1) treatment for advanced non-small-cell lung cancer (NSCLC) has improved the survival of patients. However, a substantial percentage of patients do not respond to this treatment. We examined the use of DNA methylation profiles to determine the efficacy of anti-PD-1 treatment in patients recruited with current stage IV NSCLC. METHODS: In this multicentre study, we recruited adult patients from 15 hospitals in France, Spain, and Italy who had histologically proven stage IV NSCLC and had been exposed to PD-1 blockade during the course of the disease. The study structure comprised a discovery cohort to assess the correlation between epigenetic features and clinical benefit with PD-1 blockade and two validation cohorts to assess the validity of our assumptions. We first established an epigenomic profile based on a microarray DNA methylation signature (EPIMMUNE) in a discovery set of tumour samples from patients treated with nivolumab or pembrolizumab. The EPIMMUNE signature was validated in an independent set of patients. A derived DNA methylation marker was validated by a single-methylation assay in a validation cohort of patients. The main study outcomes were progression-free survival and overall survival. We used the Kaplan-Meier method to estimate progression-free and overall survival, and calculated the differences between the groups with the log-rank test. We constructed a multivariate Cox model to identify the variables independently associated with progression-free and overall survival. FINDINGS: Between June 23, 2014, and May 18, 2017, we obtained samples from 142 patients: 34 in the discovery cohort, 47 in the EPIMMUNE validation cohort, and 61 in the derived methylation marker cohort (the T-cell differentiation factor forkhead box P1 [FOXP1]). The EPIMMUNE signature in patients with stage IV NSCLC treated with anti-PD-1 agents was associated with improved progression-free survival (hazard ratio [HR] 0·010, 95% CI 3·29 × 10-4-0·0282; p=0·0067) and overall survival (0·080, 0·017-0·373; p=0·0012). The EPIMMUNE-positive signature was not associated with PD-L1 expression, the presence of CD8+ cells, or mutational load. EPIMMUNE-negative tumours were enriched in tumour-associated macrophages and neutrophils, cancer-associated fibroblasts, and senescent endothelial cells. The EPIMMUNE-positive signature was associated with improved progression-free survival in the EPIMMUNE validation cohort (0·330, 0·149-0·727; p=0·0064). The unmethylated status of FOXP1 was associated with improved progression-free survival (0·415, 0·209-0·802; p=0·0063) and overall survival (0·409, 0·220-0·780; p=0·0094) in the FOXP1 validation cohort. The EPIMMUNE signature and unmethylated FOXP1 were not associated with clinical benefit in lung tumours that did not receive immunotherapy. INTERPRETATION: Our study shows that the epigenetic milieu of NSCLC tumours indicates which patients are most likely to benefit from nivolumab or pembrolizumab treatments. The methylation status of FOXP1 could be associated with validated predictive biomarkers such as PD-L1 staining and mutational load to better select patients who will experience clinical benefit with PD-1 blockade, and its predictive value should be evaluated in prospective studies. FUNDING: "Obra Social" La Caixa, Cellex Foundation, and the Health and Science Departments of the Generalitat de Catalunya.

Optimization of RAS/BRAF Mutational Analysis Confirms Improvement in Patient Selection for Clinical Benefit to Anti-EGFR Treatment in Metastatic Colorectal Cancer.

In metastatic colorectal cancer (mCRC), recent studies have shown the importance to accurately quantify low-abundance mutations of the RAS pathway because anti-EGFR therapy may depend on certain mutation thresholds. We aimed to evaluate the added predictive value of an extended RAS panel testing using two commercial assays and a highly sensitive and quantitative digital PCR (dPCR). Tumor samples from 583 mCRC patients treated with anti-EGFR- (n = 255) or bevacizumab- (n = 328) based therapies from several clinical trials and retrospective series from the TTD/RTICC Spanish network were analyzed by cobas, therascreen, and dPCR. We evaluated concordance between techniques using the Cohen kappa index. Response rate, progression-free survival (PFS), and overall survival (OS) were correlated to the mutational status and the mutant allele fraction (MAF). Concordance between techniques was high when analyzing RAS and BRAF (Cohen kappa index around 0.75). We observed an inverse correlation between MAF and response in the anti-EGFR cohort (P < 0.001). Likelihood ratio analysis showed that a fraction of 1% or higher of any mutated alleles offered the best predictive value. PFS and OS were significantly longer in RAS/BRAF wild-type patients, independently of the technique. However, the predictability of both PFS and OS were higher when we considered a threshold of 1% in the RAS scenario (HR = 1.53; CI 95%, 1.12-2.09 for PFS, and HR = 1.9; CI 95%, 1.33-2.72 for OS). Although the rate of mutations observed among techniques is different, RAS and BRAF mutational analysis improved prediction of response to anti-EGFR therapy. Additionally, dPCR with a threshold of 1% outperformed the other platforms. Mol Cancer Ther; 16(9); 1999-2007. ©2017 AACR.

Lymphangioleiomyomatosis Biomarkers Linked to Lung Metastatic Potential and Cell Stemness.

Lymphangioleiomyomatosis (LAM) is a rare lung-metastasizing neoplasm caused by the proliferation of smooth muscle-like cells that commonly carry loss-of-function mutations in either the tuberous sclerosis complex 1 or 2 (TSC1 or TSC2) genes. While allosteric inhibition of the mechanistic target of rapamycin (mTOR) has shown substantial clinical benefit, complementary therapies are required to improve response and/or to treat specific patients. However, there is a lack of LAM biomarkers that could potentially be used to monitor the disease and to develop other targeted therapies. We hypothesized that the mediators of cancer metastasis to lung, particularly in breast cancer, also play a relevant role in LAM. Analyses across independent breast cancer datasets revealed associations between low TSC1/2 expression, altered mTOR complex 1 (mTORC1) pathway signaling, and metastasis to lung. Subsequently, immunohistochemical analyses of 23 LAM lesions revealed positivity in all cases for the lung metastasis mediators fascin 1 (FSCN1) and inhibitor of DNA binding 1 (ID1). Moreover, assessment of breast cancer stem or luminal progenitor cell biomarkers showed positivity in most LAM tissue for the aldehyde dehydrogenase 1 (ALDH1), integrin-ß3 (ITGB3/CD61), and/or the sex-determining region Y-box 9 (SOX9) proteins. The immunohistochemical analyses also provided evidence of heterogeneity between and within LAM cases. The analysis of Tsc2-deficient cells revealed relative over-expression of FSCN1 and ID1; however, Tsc2-deficient cells did not show higher sensitivity to ID1-based cancer inhibitors. Collectively, the results of this study reveal novel LAM biomarkers linked to breast cancer metastasis to lung and to cell stemness, which in turn might guide the assessment of additional or complementary therapeutic opportunities for LAM.

HER-2/neu status and response to CMF: retrospective study in a series of operable breast cancer treated with primary CMF chemotherapy.

PURPOSE: Primary chemotherapy brings the opportunity for an early and accurate assessment of response and offers an ideal model to search for new predictors of response. HER-2/neu is one of the most studied genes for this purpose. PATIENTS AND METHODS: Her-2/neu was tested in a non-randomized series of 300 patients with operable breast carcinomas treated with primary CMF. Response was assessed by mammography. Disease-free survival (DFS) and overall survival (OS) were calculated after a mean follow-up of 116 months. Statistical analysis was performed to study the association between HER-2/neu status and response to CMF. RESULTS: Overexpression/amplification was found in 23.66% cases. Univariate analysis showed that response was similar in HER-2/neu positive and negative tumors (51.38 vs. 47.36%, P = 0.6). Triple negative tumors (ER, PR and HER-2/neu negative) presented the highest response rate (64.9%). By multivariate analysis, response was significantly correlated to higher nuclear grade and negative estrogen receptor status (P = 0.02 and 0.007, respectively). Patients with HER-2/neu positive tumors presented shorter survival rates (P = 0.06). Patients with response to CMF showed a better survival over non-responders independent of Her-2/neu status. Patients with the combination of response to CMF and Her-2/neu negative tumors presented the best outcome. On the other hand, the association of no response to CMF and positive Her-2/neu score was statistically related to poor DFS and OS. CONCLUSIONS: CMF indication is independent of Her-2/neu status.

Predictive value of HER-2 and Topoisomerase IIalpha in response to primary doxorubicin in breast cancer.

AIM: To study the predictive role of HER-2 and Topoisomerase IIalpha (TOP2A) in response to primary doxorubicin. METHODS: Two hundred and thirty-two patients with operable breast cancer were treated with doxorubicin prior to surgery. ER, PgR, grade, Ki-67 and HER-2 status were prospectively assessed. HER-2 overexpression was evaluated with immunohistochemistry; positive cases were then studied for gene copy number of HER-2, TOP2A and chromosome 17 centromere by chromogenic in situ hybridisation. Clinical response was assessed by mammography. Pathological response was evaluated as the percentage of tumour replaced by changes due to chemotherapy. RESULTS: HER-2 amplification was associated with clinical response (p=0.04). ER and PgR negativity, high Ki-67 and HER-2 amplification significantly correlated to pathological response (p<0.05). Tumours with coamplification of HER-2 and TOP2A showed a higher percentage of pathological changes (p=0.6). However, in the multivariate analysis for complete pathological response, ER negativity and high Ki-67 index were the only parameters that maintained statistical significance. CONCLUSION: HER2 and Topoisomerase IIalpha amplification failed to show an association with pathological response to doxorubicin, whereas ER negativity and a high proliferation rate were predictive of complete pathological response to this regime.

Primary chemotherapy with cyclophosphamide, methotrexate, and 5-fluorouracil in operable breast carcinoma.

BACKGROUND: Primary chemotherapy (PC) is becoming an accepted practice to treat large tumors to avoid mastectomies and as a surrogate of outcome. METHODS: A series of 305 patients with tumors >3 cm with T2-3N0-1M0 classification were treated with a multimodal approach that consisted of 3 courses of primary cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) followed by appropriate local treatment and 3 more courses of CMF or 4 courses of doxorubicin. Response was assessed by mammography. RESULTS: The overall response rate was 48% (a 3% pathologic complete response rate). Conservative surgery was achieved in 79.64% of the patients with a low rate of local disease recurrences (5%). Toxicity was minimal. With a median follow-up of 104 months, the 8-year disease-free survival (DFS) rate was 57.63% and the 8-year overall survival (OS) was 67.65%. The DFS and OS rates for patients with a clinical response were significantly longer, i.e., 70% (P=0.0048) and 90% (P=0.0042), respectively. CONCLUSIONS: PC with CMF was feasible. A high rate of breast-conservative surgery was achieved. The current results stressed the value of PC to increase conservative surgery and as a predictor of outcome.

Algorithm for the diagnosis of HER-2/neu status in breast-infiltrating carcinomas.

Determination of HER-2/neu overexpression/amplification is becoming increasingly important. The aim of this study is to elaborate an algorithm for the diagnosis of Her-2/neu status in breast-infiltrating carcinomas. Three hundred five breast-infiltrating carcinomas were selected to determine HER-2/neu overexpression by immunohistochemistry with two different methods: the monoclonal antibody CB11 and the HercepTest. Fluorescence in situ hybridization (FISH) was performed in a subgroup of those cases. Time-consuming and reagent costs were calculated for each of the procedures. HER-2/neu overexpression was found in 16% and 33% of the tumors with the monoclonal antibody (mAb) CB11 and with the HercepTest, respectively. There were 50 cases with immunohistochemical discordant results; most of them were HercepTest score 2+/mAb CB11 negative (37/50). Of those cases, only 27% presented gene amplification. The algorithm consisted of testing all the specimens with the mAb CB11 for selection of positive cases, negative cases are confirmed with the HercepTest, and FISH is performed only in those cases with immunohistochemical discordant results. The algorithm rate of HER-2/neu positivity in our series was 22%. Time and costs are reduced by 60% and 41%, respectively, compared to FISH. The use of the algorithm is feasible, accurate, and cost-effective in relation to FISH.