Discordances in HER2 status between primary gastric cancer and corresponding metastatic sites

[Standardized and quality-assured predictive PD-L1 testing in the upper gastrointestinal tract. German version]

As a result of the high approval dynamics and the growing number of immuno-oncological therapy concepts, the complexity of therapy decisions and control in the area of carcinomas of the esophagus, gastroesophageal junction and stomach is constantly increasing. Since the treatment indication for PD‑1 inhibitors that are currently approved in the European Union is often linked to the expression of PD-L1 (programmed cell death-ligand 1), the evaluation of tissue-based predictive markers by the pathologist is of crucial importance for treatment stratification. Even though the immunohistochemical analysis of the PD-L1 expression status is one of the best studied, therapy-relevant biomarkers for an immuno-oncological treatment, due to the high heterogeneity of carcinomas of the upper gastrointestinal tract, there are challenges in daily clinical diagnostic work with regard to implementation, standardization and interpretation of testing. An interdisciplinary group of experts from Germany has taken a position on relevant questions from daily pathological and clinical practice, which concern the starting material, quality-assured testing and the interpretation of pathological findings, and has developed recommendations for structured reporting.

Standardized and quality-assured predictive PD-L1 testing in the upper gastrointestinal tract

As a result of the high approval dynamics and the growing number of immuno-oncological concepts, the complexity of treatment decisions and control in the area of cancers of the esophagus, gastroesophageal junction and stomach is constantly increasing. Since the treatment indication for PD-1 inhibitors that are currently approved in the European Union is often linked to the expression of PD-L1 (programmed cell death-ligand 1), the evaluation of tissue-based predictive markers by the pathologist is of crucial importance for treatment stratification. Even though the immunohistochemical analysis of the PD-L1 expression status is one of the best studied, therapy-relevant biomarkers for an immuno-oncological treatment, due to the high heterogeneity of carcinomas of the upper gastrointestinal tract, there are challenges in daily clinical diagnostic work with regard to implementation, standardization and interpretation of testing. An interdisciplinary group of experts from Germany has taken a position on relevant questions from daily pathological and clinical practice, which concern the starting material, quality-assured testing and the interpretation of pathological findings, and has developed recommendations for structured reporting.

Discrepancies in Hormone Receptor and HER2 Expression between Malignant Serous Effusions and Paired Tissues from Primary or Recurrent Breast Cancers

INTRODUCTION

Immunohistochemistry (IHC) for the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) biomarkers has prognostic and therapeutic value in breast cancer. This study aimed to compare the expression of ER, PR, and HER2 between paired malignant effusions and tissue samples of breast cancer.

METHODS

Our electronic archive was searched for all effusions diagnosed as breast carcinomas within a pre-defined period (January 2018-October 2021). Next, their cell blocks (CBs) were subjected to ER, PR, HER2 IHC, or in situ hybridization, in addition to EGFR IHC. The expression of hormone receptors (HRs) and HER2 was subsequently compared between tissue and effusion cytology samples derived from the same patients.

RESULTS

Only 2/76 (2.6%) of the breast cancer patients analyzed showed a malignant effusion at their initial presentation. ER, PR, and HER2 discordance rates between paired malignant effusions and tissue samples obtained at initial diagnosis were 24.3% (17/73), 40.8% (29/71), and 9.1% (6/66), respectively. The HR-/HER2- status was found more often at effusions compared to paired tissue biopsies obtained at initial diagnosis (30/70 vs. 17/70; p < 0.001). In addition, the HR-/HER2- status was significantly associated with an earlier development of a malignant effusion, when found at initial diagnosis (p < 0.001; log-rank test), first recurrence/metastasis (either solid or effusion) (p = 0.012; log-rank test), effusion samples (p = 0.007; log-rank test), and any tumor sample obtained (p = 0.009; log-rank test). Lastly, EGFR overexpression in the HR-/HER2- effusion samples was significantly associated with a shorter post-effusion survival (p = 0.019; log-rank test).

CONCLUSION

Serous effusion cytology provides high-quality material for ancillary techniques, especially when CBs are prepared, reflecting cancer heterogeneity.

Detailed curriculum vitae of HER2-targeted therapy

With the booming development of precision medicine, molecular targeted therapy has been widely used in clinical oncology treatment due to a smaller number of side effects and its superior accuracy compared to that of traditional strategies. Among them, human epidermal growth factor receptor 2 (HER2)-targeted therapy has attracted considerable attention and has been used in the clinical treatment of breast and gastric cancer. Despite excellent clinical effects, HER2-targeted therapy remains in its infancy due to its resulting inherent and acquired resistance. Here, a comprehensive overview of HER2 in numerous cancers is presented, including its biological role, involved signaling pathways, and the status of HER2-targeted therapy.

Discordances in expression of human epidermal growth factor receptor 2 between primary and metastatic uterine carcinosarcoma: A proposal for HER2-targeted therapy specimen selection

Uterine carcinosarcoma (UCS) frequently expresses human epidermal growth factor receptor 2 (HER2) and metastasizes. However, little is known about changes in the HER2 expression status in metastatic lesions and its impact on clinical outcomes. In 41 patients with synchronous or metachronous metastases and matched primary UCSs, we assessed the HER-2 expression using immunohistochemistry and scored it per the 2016 American Society of Clinical Oncology/College of American Pathologists guidelines, modified for UCS. We compared HER2 scores between paired primary and metastatic lesions and reviewed the association between clinicopathological characteristics and impact on overall survival. HER2 scores of 3+, 2+, 1+, and 0 were observed in 12.2 %, 34.2 %, 26.8 %, and 26.8 % of primary tumors, respectively, and 9.8 %, 19.5 %, 43.9 %, and 26.8 % of metastatic tumors, respectively. HER2 intratumoral heterogeneity occurred in 46.3 % and 19.5 % of the primary and metastatic lesions, respectively. The agreement rate of the HER2 score was 34.2 % in the four-tiered scale, while it was 70.7 % in the two-tiered scale (score 0 vs. score ≥ 1+) with fair agreement (к = 0.26). Patients with HER2 discordance showed significantly shorter overall survival (hazard ratios = 2.38, 95 % confidence interval 1.01-5.5, p = 0.049). HER2 discordance was not associated with specific clinicopathological characteristics. Discordance in HER2 status between primary and metastatic tumors in UCS was frequently observed regardless of clinicopathological characteristics and was a poor prognostic factor. Even if one tumor (primary or metastatic) is HER2 negative, HER2 testing of other tumors may be beneficial in terms of patient treatment options.

Biomarkers expression among paired serous ovarian cancer primary lesions and their peritoneal cavity metastases in treatment-naïve patients: A single-center study

Background

High‐grade serous ovarian carcinoma (HGSOC), the most common histologic subtype of ovarian epithelial cancer, is associated with treatment resistance, enhanced recurrence rates, and poor prognosis. HGSOCs often metastasize to the peritoneal cavity, while fluid cytology examination could identify such metastases. This retrospective study aimed to identify potential biomarker discrepancies between paired HGSOC primary tissues and metastatic peritoneal fluid cytology samples, processed as cell blocks (CBs).

Methods

Twenty‐four pairs of formalin‐fixed, paraffin‐embedded primary tissues and metastatic CBs from an equal number of treatment‐naïve patients were used, and immunohistochemistry (IHC) for epidermal growth factor receptor (EGFR), human epidermal growth factor receptor, programmed cell death‐1 ligand 1 (PD‐L1), and CD147 was applied.

Results

13/24 pairs showed discordant EGFR IHC results; in all these 13 patients, EGFR was positive (≥1+ membranous staining intensity found in at least 10% of the cancer cells) in the peritoneal, yet negative in the primary tissue samples. Notably, EGFR IHC was positive in 15/24 of the metastatic, whereas in just 2/24 of the primary HGSOC samples (p < 0.001). Although most PD‐L1 results were concordant, 5/24 and 6/24 pairs exhibited discordant results when stained with the E1L3N and 22C3 clones, respectively. Lastly, CD147 overexpression was found more often in the metastatic rather than the matched primary HGSOCs stained with CD147, though the difference was not significant.

Conclusions

Cytology from effusions could be considered for biomarker testing when present, even when tissue from the primary cancer is also available and adequately cellular, as it could provide additional information of potential clinical significance.

Multimodal treatment in oligometastatic gastric cancer

Gastric cancer is generally diagnosed at an advanced stage, especially in countries without screening programs. Previously, the metastatic stage was synonymous with palliative management, and surgical indications were only for symptomatic relief. However, this therapeutic option is associated with poor prognosis. A subgroup of patients with limited metastatic disease could benefit from intensive treatment. A combination of chemotherapy, immunotherapy, and targeted therapy could help either maintain a resectable state for oligometastatic disease or diminish the metastasis size to obtain a complete resection configuration. This latter strategy is known as conversion therapy and has growing evidence with favorable outcomes. Oncosurgical approach of metastatic disease could prolong survival in selected patients. The challenge for the surgeon and oncologist is to identify these specific patients to offer the best multimodal management. We review in this article the actual evidence for the treatment of oligometastatic gastric cancer with curative intent.

Trastuzumab deruxtecan for the treatment of HER2-positive advanced gastric cancer: a clinical perspective

Human epidermal growth factor receptor 2 (HER2)-positive gastric cancer is a subtype for which new drugs and specific treatment strategies should be developed. Trastuzumab deruxtecan (T-DXd) is a novel HER2-targeted antibody-drug conjugate containing topoisomerase I inhibitor as a payload. In the randomized phase 2 study (DESTINY-Gastric01) for HER2-positive advanced gastric or gastroesophageal junction cancer (AGC), patients treated with T-DXd showed a significantly higher response rate compared with the chemotherapy of physician's choice, associated with remarkably prolonged progression-free and overall survival. T-DXd also exhibits anti-tumor activity to HER2-negative tumor cells close to HER2-positive cells (so-called bystander killing effect). T-DXd was effective even for HER2-low expressing breast and gastric cancer in several clinical studies. Taking advantage of these strong points and synergism with other cytotoxic, molecular-targeted and immunological agents, it is expected that T-DXd will bring further progression in treatment both for strongly and weakly HER2 positive AGC in various treatment settings including perioperative chemotherapy.

Detection of ERBB2 (HER2) Gene Amplification Events in Cell-Free DNA and Response to Anti-HER2 Agents in a Large Asian Cancer Patient Cohort

Background: HER2 antagonists have marked activity and are approved for the treatment of HER2 overexpressing breast and gastric cancers. Recent studies have shown that ERBB2 (HER2) gene amplification and overexpression may also be actionable in other tumor types. Inter- and intratumoral heterogeneity in HER2 status, however, poses a significant challenge in identifying patients that may benefit from HER2-targeted therapies. ERBB2 amplification as identified by circulating cell-free DNA (cfDNA), which circumvents tissue heterogeneity issues, is emerging as a robust biomarker predictive of response to anti-HER2 agents. Here, the prevalence and genomic landscape of ERBB2 alterations detectable by next-generation sequencing (NGS) of cfDNA was evaluated in a large cohort of Asian patients with advanced solid tumors. Methods: Results were queried for consecutive patients (n = 469) tested by a comprehensive 70/73-gene cfDNA NGS assay (Guardant360®) between November 2015 and June 2018. Patients with ERBB2 gene alterations including copy number amplifications (CNAs), single nucleotide variants (SNVs), and insertion-deletions (indels) were identified. Results: ERBB2 alterations were detected in 52 patients (11.1%); ERBB2 SNVs, CNAs, and indels were found in 27 (5.8%), 27 (5.8%), and 10 (2.1%) patients, respectively. ERBB2 amplification was most frequently identified in gastric (21.4%; 6/28), colorectal (11.1%; 5/45), lung (3.9%; 9/231), and breast (3.2%; 1/31) cancer patients. ERBB2 amplification was often mutually exclusive with other oncogenic alterations in gastric (83.3%; 5/6) and colorectal (60%; 3/5) cancer patients. ERBB2 copy number gains were also highest in gastric and colorectal cancers (median 4.8 and 6.6, respectively). We further report two cases of advanced gastric cancer patients, one treatment naïve, and the other having failed four lines of therapy, whose ERBB2 CNAs were identified by cfDNA and derived clinical benefit from HER2-based therapies. Conclusion: Our data indicate that ERBB2 amplification is a common event in solid tumors among Asian cancer patients. High ERBB2 incidence and copy number gains were observed in gastric and colorectal cancer patients, often in the absence of other oncogenic mutations, underscoring its likely role as the driver alteration in those settings. Finally, we show the potential of comprehensive cfDNA testing in identifying patients who are most likely to benefit from HER2-targeted therapies.

Targeting HER2-positive gastric cancer with a novel 18F-labeled ZHER2:342 probe

To realize the diagnosis of HER2-positive gastric cancer via PET imaging, herein, a new kind of ¹⁸F-labeled HER2 affibody probe was created; the bifunctional maleimide derivative 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA-MAL) was first coupled to a polypeptide, and the resulting compound was subsequently labeled with the ¹⁸FAl complex. The binding characteristics of the probe were assessed using both in vitro studies and in vivo microPET imaging and biodistribution experiments. Immunohistochemical staining was performed to confirm the expression level of HER2 in the studied cell lines and tumors. The probe was successfully produced with the radiochemical purity of more than 95%. The NCI N87 cell-associated radioactivity was 19.31 ± 1.01% AD, and it decreased to 0.83 ± 0.04% AD per 10⁶ cells after blocking HER2 as early as 15 minutes post-incubation (p < 0.05). A competition binding assay between radiolabeled and non-radioactive affibody molecules with NCI N87 indicated that the IC₅₀ was 8.10 nM. The microPET imaging and biodistribution of human gastric cancer xenografts demonstrated that the probe could specifically accumulate in tumors at early time points. Protein detection confirmed a strong HER2 expression in NCIN87 and a weak HER2 expression in SGC7901. In conclusion, ¹⁸FAl-NOTA-MAL-Cys-GGGRDN(M⁰)-Z_HER2:342 was successfully prepared via a one-step method. The favorable preclinical data showed specific and effective tumor targeting capacity of the proposed probe; this revealed that the probe proposed herein might have potential application in gastric cancer imaging.

Tumor targeting of the novel ¹⁸F-labeled Z_HER2:342 probe in HER2-positive gastric cancer xenograft models.

Molecular biomarkers in gastro-esophageal cancer: recent developments, current trends and future directions

Gastro-esophageal adenocarcinomas (GEA) represent a severe global health burden and despite improvements in the multimodality treatment of these malignancies the prognosis of patients remains poor. HER2 overexpression/amplification has been the first predictive biomarker approved in clinical practice to guide patient selection for targeted treatment with trastuzumab in advanced gastric and gastro-esophageal junction cancers. More recently, immunotherapy has been approved for the treatment of GEA and PD-L1 expression is now a biomarker required for the administration of pembrolizumab in these diseases. Significant progress has been made in recent years in dissecting the genomic makeup of GEA in order to identify distinct molecular subtypes linked to distinct patterns of molecular alterations. GEA have been found to be highly heterogeneous malignances, representing a challenge for biomarkers discovery and targeted treatment development. The current review focuses on an overview of established and novel promising biomarkers in GEA, covering recent molecular classifications from TCGA and ACRG. Main elements of molecular heterogeneity are discussed, as well as emerging mechanisms of primary and secondary resistance to HER2 targeted treatment and recent biomarker-driven trials. Future perspectives on the role of epigenetics, miRNA/lncRNA and liquid biopsy, and patient-derived xenograft models as a new platform for molecular-targeted drug discovery in GEA are presented. Our knowledge on the genomic landscape of GEA continues to evolve, uncovering the high heterogeneity and deep complexity of these tumors. The availability of new technologies and the identification of promising novel biomarker will be critical to optimize targeted treatment development in a setting where therapeutic options are currently lacking. Nevertheless, clinical validation of novel biomarkers and treatment strategies still represents an issue.

PD-L1 is an independent prognostic predictor in gastric cancer of Western patients

Targeting the PD-1/PD-L1 immune checkpoint signaling is a novel promising treatment strategy in several tumor entities, and it is suggested that PD-L1/PD-1 expression is predictive for a PD-1/PD-L1 checkpoint inhibitor treatment response. We investigated the expression of PD-L1 and PD-1 by immunohistochemistry in a large and well characterized gastric cancer (GC) cohort of Caucasian patients, consisting of 465 GC samples and 15 corresponding liver metastases. Staining results were correlated with clinico-pathological characteristics and survival. PD-L1 expression was found in tumor cells of 140 GCs (30.1%) and 9 liver metastases (60%) respectively in immune cells of 411 GCs (88.4%) and 11 liver metastases (73.3%). PD-1 was expressed in tumor infiltrating lymphocytes in 250 GCs (53.8%) and in 11 liver metastases (73.3%). PD-L1 expression was significantly more prevalent in men, GCs of the proximal stomach, unclassified, papillary, Her2/neu-positive, Epstein-Barr-virus-positive, microsatellite instable, and PIK3CA-mutated GCs. A high PD-L1/PD-1 expression was associated with a significantly better patient outcome, and PD-L1 turned out to be an independent survival prognosticator. The correlation of PD-L1/PD-1 expression with distinct clinico-pathological patient characteristics may serve as a surrogate marker of PD-L1-positive GCs and may direct the use of immune checkpoint treatment strategies.

Comparison of HER2 and Lauren Classification between Biopsy and Surgical Resection Samples, Primary and Metastatic Samples of Gastric Cancer

Purpose: Patients with advanced or metastatic adenocarcinoma of the stomach or esophagogastric junction for whom trastuzumab therapy is being considered, assessment for tumor human epidermal growth factor receptor-2 (HER2) status is necessary. Can the HER2 status and Lauren classification of the biopsy sample truly represent the HER2 status in the gastric cancer?

Methods: Formalin-fixed, paraffin-embedded sections of 116 pair surgically resected and biopsy specimens as well as 80 pair primary and metastatic lesions of gastric cancer patients were analyzed. Protein expression was assessed using immunohistochemistry (IHC) and graded by the modified scoring criteria for gastric cancer. Gene amplification was evaluated by fluorescence in situ hybridization (FISH) in IHC 2+ cases.

Results: The positive rate of HER2 was 11.2% in both surgical and biopsy samples. The consistent rate of HER2 expression was 91.4% (106/116) between biopsy and surgical samples, P=0.666. The positive rate of HER2 was 20.5% in primary and 15.9% in metastatic samples, P=0.1876. The consistent rate of HER2 expression was 90.9% (40/44) between primary and metastatic samples, P=0.580. The consistent rate of Lauren classification was 64.7% (75/116) between biopsy and surgical sample, and 92.5% (74/80) between primary and metastatic samples.

Discussion: For gastric cancer, HER2 expression and Lauren classification were highly homogenous in biopsy and surgical samples, primary and their corresponding metastatic samples. The high concordance observed between these two cohorts indicated that the HER2 examination and Lauren classification of biopsy samples from the primary tumor could well represent the metastatic lesions of the patients.

Discordance in HER2 Status in Gastro-esophageal Adenocarcinomas: A Systematic Review and Meta-analysis

Trastuzumab combined with chemotherapy is standard of care for HER2 positive advanced gastro-esophageal cancers. The reported prevalence of HER2 discordance between primary tumors and corresponding metastases varies, hampering uniform patient selection for HER2 targeted therapy. This meta-analysis explores the influence of HER2 assessment methods on this discordance and investigates the prevalence of HER2 discordance in gastro-esophageal adenocarcinomas. PubMed, Embase and Cochrane databases were searched until January 2016. Differences in discordance rate between strict and broad(er) definitions of HER2 status were assessed using random-effect pair-wise meta-analysis. Random-effect single-arm meta-analyses were performed to assess HER2 discordance and the prevalence of positive and negative conversion. A significantly lower discordance rate in HER2 status between primary tumors and corresponding metastases was observed using a strict vs. broad definition of HER2 status (RR = 0.58, 95%CI 0.41-0.82), with a pooled discordance rate of 6.2% and 12.2%, respectively. Using the strict definition of HER2 assessment pooled overall discordance was 7% (95%CI 5-10%). The lowest discordance rates between primary tumors and corresponding metastasis are observed when using a strict method of HER2 positivity. Treatment outcomes of different studies will be better comparable if selection of eligible patients for HER2 targeted therapy is based on this strict definition.

Perspectives of HER2-targeting in gastric and esophageal cancer

INTRODUCTION

The blockade of HER2 signaling has significantly improved the outlook for esophagogastric cancer patients. However, targeting HER2 still remains challenging due to complex biology of this receptor in gastric and esophageal cancers. Areas covered: Here, we review complex HER2 biology, current methods of HER2 testing and tumor heterogeneity of gastroesophageal cancer. Ongoing and completed clinical research data are discussed. Expert opinion: HER2 overexpression is a validated target in gastroesophageal cancer, with therapeutic implications resulting in prolonged survival when inhibited in the front-line setting. With standardized HER2 testing in gastro-esophageal cancer, the ongoing trials are testing newer agents and combinations including combination of anti-HER2 antibodies with immunotherapy. Clonal heterogeneity and emergence of resistance will challenge our approach to treating these patients beyond the frontline settings.

The novel negative checkpoint regulator VISTA is expressed in gastric carcinoma and associated with PD-L1/PD-1: A future perspective for a combined gastric cancer therapy?

A combined blockade of V-domain Ig suppressor of T-cell activation (VISTA) and PD-1 is a promising new cancer treatment option, which was efficient in murine tumor models and is currently tested in first phase I studies. Here, we analyzed the VISTA expression in a large and well-characterized gastric cancer (GC) cohort on 464 therapy-naive GC samples and 14 corresponding liver metastases using immunohistochemistry. Staining results were correlated with clinico-pathological characteristics, genetic alterations and survival. VISTA expression in tumor cells was detected in 41 GCs (8.8%) and 2 corresponding liver metastases (14.3%). Moreover, VISTA expression in immune cells was observed in 388 GCs (83.6%) and 6 liver metastases (42.9%). VISTA expression was associated with the Laurén phenotype, tumor localization, Epstein–Barr virus infection, KRAS- and PIK3CA-mutational status and PD-L1 expression. There was no significant correlation with patient outcome. Moreover, a change of VISTA expression in immune cells during tumor progression was observed. The co-incidence of VISTA and PD-L1 expression indicates a dual immune evasion mechanism of GC tumor cells and makes GC an interesting target for novel combined immune checkpoint inhibitor treatments.

Molecular pathology in real time

With the development of sophisticated individualized therapeutic approaches, the role of pathology in classification of tumors is enormously increasing. The solely morphological characterization of neoplastic process is no more sufficient for qualified decision on optimal therapeutic approach. Thus, morphologic diagnosis must be supplemented by molecular analysis of the lesion with emphasis on the detection of status of certain markers used as predictive factors for targeted therapy. Both intrinsic and acquired types of intratumor heterogeneity have an impact at various moments of cancer diagnostics and therapy. The primary heterogeneity of neoplastic tissue represents a significant problem in patients, where only limited biopsy samples from the primary tumor are available for diagnosis, such as core needle biopsy specimens in breast cancer, transthoracic or endobronchial biopsies in lung cancer, or endoscopic biopsies in gastric cancer. Detection of predictive markers may be influenced by this heterogeneity, and the marker detection may be falsely negative or (less probably) falsely positive. In addition, as these markers are often detected in the tissue samples from primary tumor, the differences between molecular features of the primary lesion and its metastases may be responsible for failure of systemic therapy in patients with discordant phenotype between primary and metastatic disease. The fact of tumor heterogeneity must be taken into consideration already in establishing pathological diagnosis. One has to be aware that limited biopsy specimen must not always be fully representative of the entire tumor volume. To overcome these limitations, there does not exist one single simple solution. Examination of more tissue (preference of surgical resection specimens over biopsies, whenever possible), use of ultra-sensitive methods able to identify the minute subclones as a source of possible resistance to treatment, and detection of secondary molecular events from the circulating tumor cells or circulating cell-free DNA are potential solutions how to handle this issue.

HER2 Status in Gastric Cancer: Comparison between Primary and Distant Metastatic Disease

HER2 (human epidermal growth factor receptor-2) assessment in histological samples of gastric cancer is essential to determine which patients might benefit from trastuzumab therapy. HER2 is often evaluated in primary tumor even if trastuzumab therapy is used to treat metastatic disease. However, the exact relationship in terms of HER2 status between primary and metastatic tumors has not been fully clarified. We aimed to evaluate the HER2 status concordance between primary gastric cancer and corresponding distant metastasis. HER2 status was evaluated by IHC (immunohistochemistry) and/or FISH ( fluorescence in situ hybridization) in 41 patients in primary gastric cancer and in paired metastasis. HER2 was assessed according scoring criteria applied in clinical approach. HER2 positivity was found in 14,6 % primary tumors and in 24,4%corresponding metastasis. HER2 concordance rate between primary and metastasis was 80,5 % (K-value = 0,388). Eight/41 (19,5 %)cases resulted discordant: 6 patients with metastatic HER2 positive lesions were found HER2 negative in primary cancers while 2 patient HER2 positive in primary lesion showed a negative conversion in metastasis. Our results showed a good concordance in terms of HER2 status between primary and metastatic lesions, as well as in biopsy and surgical removed specimens. However, the higher rate of HER2 positive status found in metastatic lesions underlined the importance of HER2 assessment in all samples obtained from different sites of gastric cancer disease.