Synchronous appendiceal and intramucosal gastric signet ring cell carcinomas in an individual with CDH1-associated hereditary diffuse gastric carcinoma: a case report of a novel association and review of the literature. BMC Gastroenterol. 2013;13:114. [PMID: 23849133 PMCID: PMC3716915 DOI: 10.1186/1471-230x-13-114]

Hereditary Diffuse Gastric Cancer

Hereditary diffuse gastric cancer (HDGC) is a dominantly inherited cancer syndrome characterized by a high incidence of diffuse gastric cancer (DGC) and lobular breast cancer (LBC). HDGC is caused by germline mutations in 2 genes involved in the epithelial adherens junction complex, CDH1 and CTNNA1. We discuss the genetics of HDGC and the variability of its clinical phenotype, in particular the variable penetrance of advanced DGC and LBC, both within and between families. We review the pathology of the disease, the mechanism of tumor initiation, and its natural history. Finally, we describe current best practice for the clinical management of HDGC, including emerging genetic testing criteria for the identification of new families, methods for endoscopic surveillance, the complications associated with prophylactic surgery, postoperative quality of life, and the emerging field of HDGC chemoprevention.

Epidemiology and prognostic analysis of patients with pancreatic signet ring cell carcinoma: a population-based study

Background

Pancreatic signet ring cell carcinoma (PSRCC) is a rare tumour subtype with poorly understood epidemiological characteristics and prognosis. We attempted to comprehensively characterise the epidemiology and survival outcomes of PSRCC.

Methods

Patients diagnosed with PSRCC between 2000 and 2018 were identified using Surveillance, Epidemiology and End Results Stat 8.3.9.2 software. Age-adjusted incidence and survival were calculated. Survival curves were plotted using the Kaplan–Meier method, and the differences between survival curves were compared using the log-rank test. Cox proportional hazards models were used to evaluate factors that independently predict overall survival. The primary analysis was a complete case analysis; multiple imputations were employed in a sensitivity analysis.

Results

We identified 585 eligible patients with PSRCC. The overall annual incidence from 2000 to 2018 was 0.349 (95% CI, 0.321–0.379) per million population. The incidence increased significantly in patients over 55 years of age and peaked at about 80 years of age (2.12 per million). Males and Black patients had the highest incidence. The observed survival rates at 1, 2 and 5 years were 20.1, 8.3 and 3.4%, respectively. Survival analysis revealed that primary surgery and chemotherapy are effective treatments for patients with PSRCC (P < 0.05). According to multivariate Cox regression analysis, early stage and receiving surgery and chemotherapy were favourable factors (P < 0.05). Similar conclusions were drawn from the interpolated data.

Conclusions

PSRCC is a highly malignant tumour that predominates in elderly, male and Black patients. The prognosis is poor with a 5-year survival rate of 3.4%; however, multivariate analysis and adjusted models accounting for missing data revealed that early diagnosis, surgery and chemotherapy are effective in improving the prognosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02543-z.

Hereditary Diffuse Gastric Cancer: Molecular Genetics, Biological Mechanisms and Current Therapeutic Approaches

Hereditary diffuse gastric cancer is an autosomal dominant syndrome characterized by a high prevalence of diffuse gastric cancer and lobular breast cancer. It is caused by inactivating mutations in the tumor suppressor gene CDH1. Genetic testing technologies have become more efficient over the years, also enabling the discovery of other susceptibility genes for gastric cancer, such as CTNNA1 among the most important genes. The diagnosis of pathogenic variant carriers with an increased risk of developing gastric cancer is a selection process involving a multidisciplinary team. To achieve optimal long-term results, it requires shared decision-making in risk management. In this review, we present a synopsis of the molecular changes and current therapeutic approaches in HDGC based on the current literature.

Nomograms to predict individual prognosis of patients with primary signet ring cell carcinoma of the urinary bladder

Background

Signet ring cell carcinoma (SRCC) is a rare but highly malignant variant of bladder carcinoma. Nomograms have demonstrated good accuracy in predicting the prognosis and guiding the management of pure urothelial carcinoma (UC). However, no accurate and applicable nomogram has been formulated for primary SRCC cases. This study aimed to determine significant prognostic factors and to construct nomograms for predicting the survival outcomes of patients with primary SRCCs of the urinary bladder.

Methods

A total of 317 eligible patients diagnosed with SRCC were analyzed using the 2004–2016 data from the Surveillance, Epidemiology, and End Results database. Univariate and multivariate analyses were performed to explore the prognostic values. Nomograms were established to estimate the overall survival (OS) and cancer-specific survival (CSS) based on the Cox regression results. The performance of SRCC nomograms was evaluated using the concordance index and calibration curves. Survival curves were applied according to various surgical methods, lymph node status, and risk groups distinguished by nomograms.

Results

Two nomograms included common indicators that were significantly associated with OS and CSS, including T stage, M stage, tumor size, surgery, and the lymph node ratio (LNR). The nomograms indicated appreciable accuracy in predicting the OS and CSS, with concordance index of 0.723 [95% confidence interval (95% CI: 0.692–0.754] and 0.740 (95% CI: 0.701–0.779), respectively. The calibration curves revealed satisfactory consistency between the prediction of deviation correction and ideal reference line.

Conclusions

The two nomograms developed in this study showed high accuracy and reliability in predicting the survival outcomes of patients with SRCC and could be used to comprehensively assess the risk of SRCC. Moreover, they could assist in the optimal treatment selection for such patients.

CDH1 Gene Mutation Hereditary Diffuse Gastric Cancer Outcomes: Analysis of a Large Cohort, Systematic Review of Endoscopic Surveillance, and Secondary Cancer Risk Postulation

Simple Summary

Some patients carry a mutated copy of the CDH1 gene that can lead to a very rare form of hereditary gastric cancer called signet-ring cell adenocarcinoma (SRCC). SRCCs rarely form visible tumors prior to spreading. Hence, patients are recommended to have prophylactic gastrectomies at a young age. Many patients wish to avoid surgery and thus have regular checks with upper endoscopy with biopsies to rule out cancer. Further, these patients may also be at risk of other cancers beyond the already known breast cancer risks, but this is not known. In this study, we show that despite systematic biopsy protocols, many early cancers might be missed on endoscopy. Therefore, patients should not rely on endoscopy to delay surgery. These patients may also be at increased risk of colorectal SRCC, which has very poor survival outcomes. To confirm this, we need a central database that captures outcomes for this patient population.

Abstract

Hereditary diffuse gastric cancer (HDGC) is a rare signet-ring cell adenocarcinoma (SRCC) linked to CDH1 (E-cadherin) inactivating germline mutations, and increasingly other gene mutations. Female CDH1 mutation carriers have additional risk of lobular breast cancer. Risk management includes prophylactic total gastrectomy (PTG). The utility of endoscopic surveillance is unclear, as early disease lacks macroscopic lesions. The current systematic biopsy protocols have unknown efficacy, and other secondary cancer risks are postulated. We conducted a retrospective study of consecutive asymptomatic HDGC patients undergoing PTG, detailing endoscopic, pathologic, and outcome results. A systematic review compared endoscopic biopsy foci detection via random sampling versus Cambridge Protocol against PTG findings. A population-level secondary-cancer-risk postulation among sporadic gastric SRCC patients was completed using the Surveillance, Epidemiology, and End Results database. Of 97 patients, 67 underwent PTG, with 25% having foci detection on random endoscopic biopsy despite 75% having foci on final pathology. There was no improvement in the endoscopic detection rate by Cambridge Protocol. The postulated hazard ratio among sporadic gastric SRCC patients for a secondary colorectal SRCC was three-fold higher, relative to conventional adenocarcinoma patients. Overall, HDGC patients should not rely on endoscopic surveillance to delay PTG, and may have secondary SRCC risks. A definitive determination of actual risk requires collaborative patient outcome data banking.

Significance of E-cadherin Gene Mutations in Patients With Hereditary Diffuse Gastric Cancer Syndrome: A Systematic Review

Gastric cancer is the third-most fatal cancer in the world. Though over the years, we saw patients mostly with intestinal type accounting for the highest mortality rate, the recent rise of the diffuse form with germline E-cadherin (CDH1) mutations has added a whole new level of interest to study in detail about the association between CDH1 and diffuse gastric cancer (DGC). This introduced a set guideline formulated by Internal Gastric Cancer Linkage Consortium (IGCLC) for patients with family history of diffuse gastric cancer and invasive lobular breast cancer (ILBC). The analysis of this link was also important to set proper management protocol for patients who were CDH1 mutation carriers which now involves genetic counselling, endoscopic surveillance and screening and prophylactic total gastrectomy (PTG). The study was conducted in accordance to the 'PRISMA guidelines for reporting systematic review and meta-analysis'. Peer-reviewed studies were included from the PubMed database and relevant articles were selected to be included in the study. Appropriate inclusion/exclusion criteria with free full text English articles were applied while selecting the articles. A total of 10 studies on review with different study populations showed that of the 42 patients who were diagnosed with diffuse gastric cancer, 88% of them showed a positive germline E-cadherin gene mutation and 100% of the CDH1 mutation carriers showed microscopic changes of signet ring cell adenocarcinoma of the stomach. The beneficial effects of PTG with better survival rates and low mortality rates has outweighed other treatment modalities. Laparoscopic approach has proved to be more useful and a safer approach for gastrectomy surgeries with better post-operative management. The need for prophylactic mastectomy is also increased in the recent times and thus this requires a new set of guidelines for ILBC patients with hereditary diffuse gastric cancer (HDGC) syndrome.

Epidemiology of Signet Ring Cell Adenocarcinomas

Signet ring cell adenocarcinomas (SRCCs) are a rare histological subtype of adenocarcinomas with a poor prognosis, typically due to advanced disease at diagnosis. A signet ring cell, mimicking its moniker, contains abundant intracytoplasmic mucin that pushes the nucleus to the periphery. In these cancers, this cell feature comprises more than 50% of the tumor. Despite predilection for the gastrointestinal tract, and in particular the stomach, primary SRCCs are also described in other sites, typically in case reports. This literature, however, lacks a standardized overview of the SRCC disease entity. Using a retrospective cohort approach, we summarize the clinicodemographic and mortality outcomes of SRCCs in thirteen primary sites, comprising 95% of all SRCCs in the Surveillance, Epidemiology, and End Results Program (SEER), a population-level cancer database covering nearly one-third of the United States population. SRCCs general trends compared to matching nonvariant adenocarcinomas are earlier age of onset, with initial presentation favoring higher rates of regional or distant disease presentation and poor tumor differentiation. After multivariable analysis, SRCCs typically have worse overall survivals, but substantial variances exist depending on tumor location. Identifying SRCCs at earlier disease stages is likely the single most important intervention to improving outcomes for these patients.

Hereditary gastric cancer: Three rules to reduce missed diagnoses

Gastric cancer remains one of the most lethal cancers. The incidence and mortality rates are quite similar. The main reason for the high mortality is diagnosis at advanced stages of disease, when treatment options are poor. One of the supposed strategies to overcome late-stage diagnosis is identifying people at high risk with the aim of establishing rigorous clinical control, including routine endoscopy and biopsies. Hereditary gastric cancer (HGC) syndromes, though representing a sizeable group to monitor for prevention or, at least, for early diagnosis, are apparently extremely rare. The low rate of HGC diagnosis might be related to the low rates of suspicion, insufficient familiarity about clinical diagnosis criteria, and the supposed conditional necessity of a molecular diagnosis. In this review, we will discuss simple measures to increase HGC diagnosis by applying three rules that might provide an opportunity for precision care to benefit the families affected by this disease.

Synchronous multiple primary gastrointestinal cancers with CDH1 mutations: A case report

BACKGROUND

Synchronous multiple primary cancers (SMPC) mean two or more malignant tumors occurring simultaneously and with different origins no matter what types they are or where they are located. The carcinogenesis of SMPC often involves variations of some specific genes. However, the correlation between CDH1 mutations and synchronous multiple primary gastrointestinal cancers is largely unknown.

CASE SUMMARY

A 62-year-old woman had sustained abdominal pain for one week and visited our hospital. Gastrointestinal endoscopy revealed multiple small polypoid lesions in both the stomach and colorectum. Computed tomography and laboratory results were within normal limits. Pathological evaluation confirmed signet ring cell carcinoma without obvious metastatic evidence. Malignant cells showed negativity for E-cadherin and positivity for β-catenin in the cytoplasm and nucleus. DNA sequencing performed on paraffin-embedded tissue revealed two exactly coincident alterations in CDH1, C.57T>G and C.1418A>T.

CONCLUSION

This case suggests that the combination of CDH1 mutations and WNT/β-catenin signaling activation contributes to the carcinogenesis of gastrointestinal SMPC.

The Impact of Epidemiological Factors and Treatment Interventions on Survival in Patients With Signet Ring Cell Carcinoma of the Pancreas

OBJECTIVES

Primary pancreatic signet ring cell carcinoma (SRCC) is a rare histologic variant of pancreatic carcinoma. A population-based analysis of pancreatic SRCC was performed to determine the predictive effects of epidemiological factors and treatment interventions on overall survival (OS) and disease-specific survival (DSS).

MATERIALS AND METHODS

The Surveillance, Epidemiology, and End Results registry was searched for pancreatic SRCC cases diagnosed between January 1, 1973 and December 31, 2013. Statistical analysis was performed using the Fisher exact test, χ(2) analysis, Kaplan-Meier method, log-rank test, and Cox proportional hazards regression.

RESULTS

The mean age among 497 patients was 66.6 years (SD, 11.9). Most patients were white (82.7%) and male (54.5%). The 1-, 2-, and 5-year OS rates were 17%, 9%, and 4%, respectively, while the corresponding 1-, 2-, and 5-year rates for DSS were 18%, 10%, and 5%, respectively. On univariable analysis; age, site, grade, stage, and treatment were predictive of OS and DSS (P<0.05). On multivariable analysis; radiation improved OS and DSS (adjusted hazard ratio [aHR], 0.592 and 0.589, respectively), pancreatectomy improved OS and DSS (aHR, 0.360 and 0.355, respectively), and combination therapy improved OS and DSS (aHR, 0.295 and 0.286, respectively). Age, site, and stage were also independent predictors of OS and DSS. Subgroup analysis demonstrated treatment to be an independent predictor of OS and DSS in localized/regional disease, in distant disease, and in patients diagnosed between 2000 and 2013.

CONCLUSIONS

Age, site, stage, and treatment independently predict OS and DSS in pancreatic SRCC.

Clinical spectrum and pleiotropic nature of CDH1 germline mutations

CDH1 encodes E-cadherin, a key protein in adherens junctions. Given that E-cadherin is involved in major cellular processes such as embryogenesis and maintenance of tissue architecture, it is no surprise that deleterious effects arise from its loss of function. E-cadherin is recognised as a tumour suppressor gene, and it is well established that CDH1 genetic alterations cause diffuse gastric cancer and lobular breast cancer—the foremost manifestations of the hereditary diffuse gastric cancer syndrome. However, in the last decade, evidence has emerged demonstrating that CDH1 mutations can be associated with lobular breast cancer and/or several congenital abnormalities, without any personal or family history of diffuse gastric cancer. To date, no genotype–phenotype correlations have been observed. Remarkably, there are reports of mutations affecting the same nucleotide but inducing distinct clinical outcomes. In this review, we bring together a comprehensive analysis of CDH1-associated disorders and germline alterations found in each trait, providing important insights into the biological mechanisms underlying E-cadherin’s pleiotropic effects. Ultimately, this knowledge will impact genetic counselling and will be relevant to the assessment of risk of cancer development or congenital malformations in CDH1 mutation carriers.

CDH1 Gene and Hereditary Diffuse Gastric Cancer Syndrome: Molecular and Histological Alterations and Implications for Diagnosis And Treatment

Gastric cancer, a group of common malignancies, results in the most cancer mortality worldwide after only lung and colorectal cancer. Although familial gastric cancers have long been recognized, it was not until recently that they were discovered to be associated with mutations of specific genes. Mutations of CDH1, the gene encoding E-cadherin, are the most common germline mutations detected in gastric cancer and underlie hereditary diffuse gastric cancer (HDGC) syndrome. All reported HDGCs are the pure diffuse type by Lauren classification and are associated with dismal prognosis once the tumor invades the submucosa. Because CDH1 germline mutations are inherited in an autosomal-dominant fashion and have high penetrance, the International Gastric Cancer Linkage Consortium (IGCLC) developed criteria to facilitate the screening of CDH1 mutation carriers; these criteria have been proven to have excellent sensitivity and specificity. Recent histologic studies suggest that HDGC progresses through several stages. Even when the tumor becomes "invasive" in lamina propria, it may stay indolent for a long time. However, the molecular mechanisms that induce the transitions between stages and determine the length of the indolent phase remain to be determined. Although the standard management for CDH1 mutation carriers is prophylactic total gastrectomy, many questions must be answered before the surgery can be done. These include the optimal surveillance strategy, the best strategy to choose surgical candidates, and the ideal time to perform surgery. In addition to increasing the risk of gastric cancer, CDH1 germline mutations also increase the risk of invasive lobular carcinoma of the breast, and possibly colorectal adenocarcinoma, and are associated with blepharocheilodontic syndrome (a congenital development disorder). However, the optimal management of these conditions is less established owing to insufficient data regarding the risk of cancer development. This review focuses on molecular and histological findings in HDGC, as opposed to sporadic diffuse gastric cancer, and their implications for the management of CDH1 mutation carriers and the diagnosis and treatment of HDGC. Other conditions associated with CDH1 germline mutations and future research directions are also discussed.

Pathological features of total gastrectomy specimens from asymptomatic hereditary diffuse gastric cancer patients and implications for clinical management

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant syndrome characterised by multigenerational diffuse gastric cancer, and is mainly caused by germline alterations in the CDH1 gene. Currently, endoscopy has limited diagnostic accuracy, and total gastrectomy (TG) is the treatment of choice for asymptomatic CDH1 carriers. In this study, we aimed to obtain a better understanding of HDGC syndrome by exploring the histopathological findings of TG specimens from asymptomatic HDGC patients. A comprehensive literature review was carried out, searching for TGs performed in asymptomatic HDGC patients. Fourteen unpublished cases, analysed in our institution, were also included. The series encompassed 174 CDH1 carriers. Preoperative endoscopic biopsies were positive in 28.3%. A macroscopic lesion was apparent in 11.7% of TGs. Histopathological analysis revealed intraepithelial lesions and/or intramucosal signet ring cell carcinoma in 87.9% of TGs. When we explored the type of protocol used for handling the specimens, we found that microscopic cancer foci were detected in 95.3% of TGs when a total-embedding protocol (assessment of the totality of gastric mucosa) was applied, and only in 62.5% when no specific protocol was used (P < 0.001). Helicobacter pylori infection was found in 23.4% cases. In conclusion, a thorough histopathological examination of gastric mucosa remains the gold standard for detection of cancer foci in HDGC gastrectomy specimens, requiring experienced pathologists for an accurate diagnosis. A better understanding of the natural history of HDGC will enable better clinical management of HDGC patients, particularly regarding the optimal timing for the performance of TG.

Hereditary diffuse gastric cancer: how to look for and how to manage it

With a current molecular revolution, hereditary gastric cancer represents a small group of patients that require a special multidisciplinary treatment. Surgeons being a member of the multidisciplinary teams are an important part of the diagnosis, treatment and follow-up of these patients. The prophylactic nature of the gastrectomy with all different problems associated with this procedure need to be widely discussed with patients. We present a review of how to look for and how to manage a hereditary diffuse-type gastric cancer.

Synchronous occurrence of hereditary gastric adenocarcinoma, gastrointestinal stromal tumor, and esophageal small cell and squamous carcinoma in situ: an extremely rare case report

BACKGROUND

Hereditary diffuse gastric carcinoma (HDGC) accounts for 1-3% of all gastric carcinomas. Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the gastrointestinal (GI) tract but they comprise fewer than 1% of all GI malignancies. Small-cell carcinoma (SmCC) is a rare histological type of esophageal carcinoma, accounting for 0.4% to 2.8% of all esophageal tumors. Co-occurrence of SmCC with esophageal tumors caused by squamous carcinoma is also very uncommon. Although multiple primary malignancies are no longer rare in clinical practice, the simultaneous appearance of HDGC, GIST, esophageal small cell and squamous carcinoma in situ is extremely rare and very few cases have been reported.

CASE PRESENTATION

We present a case of a 53 year-old woman with synchronous occurrence of four malignancies including HDGC, GIST, esophageal small cell- and local squamous carcinoma in situ. A total gastrectomy with D2 lymph node dissection and postoperative adjuvant chemotherapy with oxaliplatin and paclitaxel liposome were performed. After a 1-year follow-up, this patient was still in good condition with no evidence of recurrence.

CONCLUSION

This is the unique case that describes the co-existence of the aforementioned four types of neoplasm. This case demonstrates that a diagnosis of gastric cancer does not preclude the presence of other malignancies and every case should be thoroughly analyzed to avoid missing other problems, which may worsen the prognosis.

Hereditary diffuse gastric cancer: updated clinical guidelines with an emphasis on germline CDH1 mutation carriers

Germline CDH1 mutations confer a high lifetime risk of developing diffuse gastric (DGC) and lobular breast cancer (LBC). A multidisciplinary workshop was organised to discuss genetic testing, surgery, surveillance strategies, pathology reporting and the patient's perspective on multiple aspects, including diet post gastrectomy. The updated guidelines include revised CDH1 testing criteria (taking into account first-degree and second-degree relatives): (1) families with two or more patients with gastric cancer at any age, one confirmed DGC; (2) individuals with DGC before the age of 40 and (3) families with diagnoses of both DGC and LBC (one diagnosis before the age of 50). Additionally, CDH1 testing could be considered in patients with bilateral or familial LBC before the age of 50, patients with DGC and cleft lip/palate, and those with precursor lesions for signet ring cell carcinoma. Given the high mortality associated with invasive disease, prophylactic total gastrectomy at a centre of expertise is advised for individuals with pathogenic CDH1 mutations. Breast cancer surveillance with annual breast MRI starting at age 30 for women with a CDH1 mutation is recommended. Standardised endoscopic surveillance in experienced centres is recommended for those opting not to have gastrectomy at the current time, those with CDH1 variants of uncertain significance and those that fulfil hereditary DGC criteria without germline CDH1 mutations. Expert histopathological confirmation of (early) signet ring cell carcinoma is recommended. The impact of gastrectomy and mastectomy should not be underestimated; these can have severe consequences on a psychological, physiological and metabolic level. Nutritional problems should be carefully monitored.

Presymptomatic identification of CDH1 germline mutation in a healthy korean individual with family history of gastric cancer

Gastric cancer (GC) is one of the most common cancers with high morbidity and mortality. Familial GC is seen in 10% of cases, and approximately 3% of familial GC cases arise owing to hereditary diffuse gastric cancer (HDGC). CDH1, which encodes the protein E-cadherin, is the only gene whose mutations are associated with HDGC. Screening for the familial GC-predisposing gene has been neglected in high-risk countries such as Korea, China, and Japan, where all the cases have been attributed to Helicobacter pylori or other carcinogens. Screening for the GC-causing CDH1 mutation may provide valuable information for genetic counseling, testing, and risk-reduction management for the as-yet unaffected family members. An asymptomatic 44-yr-old Korean male visited our genetic clinic for consultation owing to his family history of GC. Eventually, c.1018A>G in CDH1, a known disease-causing mutation, was found. As of the publication time, the individual is alive without the evidence of GC, and is on surveillance. To our knowledge, this is the first Korean case of presymptomatic detection of CDH1 mutation, and it highlights the importance of genetic screening for individuals with a family history of GC, especially in high-risk geographical areas.

Mechanisms behind signet ring cell carcinoma formation

Signet ring cell carcinomas are highly malignant dedifferentiated adenocarcinomas. There are no cell-cell interactions between these round-shaped cells. They contain huge numbers of vacuoles, filled with mucins, which are secreted from the cells. The mechanism behind this phenotype has recently begun to be elucidated. In highly differentiated adenocarcinomas the ErbB2/ErbB3 complex is activated, which is followed by phosphatidylinositol 3-kinase (PI3K) activation. p38 MAP kinase is activated downstream of PI3K and adherens junctions are disrupted via Rac1 activation. Loss of adherens junctions leads to the disappearance of tight junctions, which results in a loss of cell-cell interactions. Secretion of mucin is enhanced by activation of PI3K. One of the mucins - Muc4 - can activate ErbB2. Under normal conditions Muc4 and ErbB2 are separated by adherens and tight junctions, however in signet ring cells they are able to interact, since these junctions have been lost. Therefore, an activation loop is formed, consisting of ERbB2/ErbB3-Muc4-ErbB2/ErbB3. As a result, the ErbB2/ErbB3 signaling pathway becomes constitutively activated, cell-cell interactions are lost, and signet ring carcinomas are formed. As a result of constitutive activation of the ErbB2/ErbB3 complex, cell growth is continuously enhanced. Some signet ring cell carcinomas have been found to have mutations in the E-cadherin gene, which fits the above hypothesis.