Unveiling the clinicopathological enigma of crawling-type gastric adenocarcinoma

In this editorial we comment on the article by Xu et al.Gastric adenocarcinoma(GA)is a malignancy which arises from the gastric mucosa and encompasses heterogenous tumors with varying characteristics.There are two main classifications:Lauren’s and the World Health Organization distinguishing the diverse types of GA depending on clinical,genetic,morphological and epidemiological features.“Crawling-type”adenocarcinoma(CRA)is a subtype characterized by irregularly fused glands with low-grade cellular atypia.Moreover,CRA represents differentiated tumor cells resembling intestinal metaplasia which results in misdiagnosis.The diagnosis is of utmost importance,as well as the subclassification and thorough pathological assessment.With regard to the symptoms of GA,these depend on the stage of the disease.Diagnostic methods play a crucial role in assessing the extent of the tumor and the stage of the disease.Nevertheless,early detection of CRA remains challenging due to its histological features.In summary,CRA is a distinct type of GA with particular clinicopathological and histological characteristics.Despite its significance,it not distinguished as a subtype,resulting in diagnostic challenges.Diagnosis is based on careful observation and thorough biopsy analysis,indicating the importance of comprehensive pathological assessment.

Hepatoid adenocarcinoma of the lung:A case report

BACKGROUND Hepatoid adenocarcinoma of the lung(HAL)is a rare type of non-small cell lung cancer(NSCLC),histologically similar to hepatocellular carcinoma.HAL has high malignancy and poor prognosis,and a better treatment plan needs further study.CASE SUMMARY In order to deeply understand the occurrence and development of HAL,here we report a case of HAL with extensive metastasis of alpha fetoprotein negative KRAS A146T mutation.The patient refused chemotherapy and received one course of treatment(immune checkpoint inhibitors),and died three months later due to progressive disease.CONCLUSION HAL is a special type of NSCLC.The surgical treatment of HAL in the limited stage can achieve long-term survival,but most of them were in the advanced stage when they were found,and the prognosis was poor,which requires multidisciplinary comprehensive treatment.

Vaginal clear cell adenocarcinoma in Herlyn-Werner-Wunderlich syndrome:A case report

BACKGROUND Herlyn-Werner-Wunderlich(HWW)syndrome is a rare Müllerian duct anomaly,characterized by a combination of urogenital abnormalities.The occurrence of primary cervico-vaginal carcinomas in patients with HWW syndrome is excep-tionally rare,posing significant challenges for screening,early diagnosis,and effective management.CASE SUMMARY We report a rare case of primary clear cell carcinoma of the vagina complicated in a 40-year-old woman with HWW syndrome.The patient presented with irregular vaginal bleeding for 4 years.On gynecological examination,an oblique vaginal septum was suspected.Surgical resection of the vaginal septum revealed a com-municating fistula and a tumor on the left vagina and the left side of the septum,which was confirmed as clear cell carcinoma.One month later,she underwent a radical hysterectomy,vaginectomy,bilateral salpingo-oophorectomy,and pelvic lymph node dissection.Due to significant side effects,she completed only one course of chemotherapy.A year later,lung metastasis was detected and continued to grow.A thoracoscopic wedge resection of the right upper lobe was performed 4 years after the initial surgery.We also conducted a systemic review of the lite-rature on primary cervical or vaginal carcinoma in HWW syndrome to explore this rare entity.CONCLUSION Cervico-vaginal adenocarcinomas in patients with HWW syndrome are occult,and require early surgical intervention and regular imaging surveillance.

Clinical pathological characteristics of“crawling-type”gastric adenocarcinoma cancer:A case report

BACKGROUND Gastric cancer(GC)is a significant health problem worldwide,and early detection and accurate diagnosis are crucial for improving patient outcomes.Crawling-type gastric adenocarcinoma is a rare subtype of GC that has unique histopathological and clinical characteristics,and its diagnosis and management can be challenging.This pathological type of GC is also rare.CASE SUMMARY Here,we report the case of a patient who underwent ordinary endoscopy,na-rrow-band imaging,and endoscopic ultrasonography intending to determine the extent of tumor invasion and upper abdominal enhanced computed tomography and whether there was tumor metastasis.Then,endoscopic submucosal dissection was performed.After pathological and immunohistochemical examination,the pathological diagnosis was crawling-type gastric adenocarcinoma.This is a very rare and special pathological type of tumor.This case highlights the importance of using advanced endoscopic techniques and pathological examination in diagnosing and managing gastric crawling-type adenocarcinoma.Moreover,the findings underscore the need for continued research and clinical experience in this rare subtype of GC to improve patient outcomes.CONCLUSION The“crawling-type”GC is a rare and specific tumor pathology.It is difficult to identify and diagnose gliomas via endoscopy.The tumor is ill-defined,with a flat appearance and indistinct borders due to the lack of contrast against the background mucosa.Pathology revealed that the tumor cells were hand-like,so the patient has diagnosed with“crawling-type”gastric adenocarcinoma.

Prognostic significance of grade of malignancy based on histopathological differentiation and Ki-67 in pancreatic ductal adenocarcinoma

Objective:Tumor cell malignancy is indicated by histopathological differentiation and cell proliferation.Ki-67,an indicator of cellular proliferation,has been used for tumor grading and classification in breast cancer and neuroendocrine tumors.However,its prognostic significance in pancreatic ductal adenocarcinoma(PDAC)remains uncertain.Methods:Patients who underwent radical pancreatectomy for PDAC were retrospectively enrolled,and relevant prognostic factors were examined.Grade of malignancy(GOM),a novel index based on histopathological differentiation and Ki-67,is proposed,and its clinical significance was evaluated.Results:The optimal threshold for Ki-67 was determined to be 30%.Patients with a Ki-67 expression level>30%rather than≤30%had significantly shorter 5-year overall survival(OS)and recurrence-free survival(RFS).In multivariate analysis,both histopathological differentiation and Ki-67 were identified as independent prognostic factors for OS and RFS.The GOM was used to independently stratify OS and RFS into 3 tiers,regardless of TNM stage and other established prognostic factors.The tumor-nodemetastasis-GOM stage was used to stratify survival into 5 distinct tiers,and surpassed the predictive performance of TNM stage for OS and RFS.Conclusions:Ki-67 is a valuable prognostic indicator for PDAC.Inclusion of the GOM in the TNM staging system may potentially enhance prognostic accuracy for PDAC.

Diagnosis of poorly differentiated adenocarcinoma of the stomach by confocal laser endomicroscopy:A case report

BACKGROUND In recent years,confocal laser endomicroscopy(CLE)has become a new endoscopic imaging technology at the microscopic level,which is extensively performed for real-time in vivo histological examination.CLE can be performed to distinguish benign from malignant lesions.In this study,we diagnosed using CLE an asymptomatic patient with poorly differentiated gastric adenocarcinoma.CASE SUMMARY A 63-year-old woman was diagnosed with gastric mucosal lesions,which may be gastric cancer,in the small curvature of the stomach by gastroscopy.She consented to undergo CLE for morphological observation of the gastric mucosa.Through the combination of CLE diagnosis and postoperative pathology,the intraoperative CLE diagnosis was considered to be reliable.According to our experience,CLE can be performed as the first choice for the diagnosis of gastric cancer.CONCLUSION CLE has several advantages over pathological diagnosis.We believe that CLE has great potential in the diagnosis of benign and malignant gastric lesions.

Stereotactic body radiotherapy in pancreatic adenocarcinoma

Background:Stereotactic body radiotherapy(SBRT)in pancreatic cancer allows high delivery of radiation doses on tumors without affecting surrounding tissue.This review aimed at the SBRT application in the treatment of pancreatic cancer.Data sources:We retrieved articles published in MEDLINE/PubMed from January 2017 to December 2022.Keywords used in the search included:“pancreatic adenocarcinoma”OR“pancreatic cancer”AND“stereotactic ablative radiotherapy(SABR)”OR“stereotactic body radiotherapy(SBRT)”OR“chemoradiotherapy(CRT)”.English language articles with information on technical characteristics,doses and fractionation,indications,recurrence patterns,local control and toxicities of SBRT in pancreatic tumors were included.All articles were assessed for validity and relevant content.Results:Optimal doses and fractionation have not yet been defined.However,SBRT could be the standard treatment in patients with pancreatic adenocarcinoma in addition to CRT.Furthermore,the combination of SBRT with chemotherapy may have additive or synergic effect on pancreatic adenocarcinoma.Conclusions:SBRT is an effective modality for patients with pancreatic cancer,supported by clinical practice guidelines as it has demonstrated good tolerance and good disease control.SBRT opens a possibility of improving outcomes for these patients,both in neoadjuvant treatment and with radical intent.

Diagnostic challenges and individualized treatment of cervical adenocarcinoma metastases to the breast:A case report

BACKGROUND Cervical cancer is a rare primary tumor resulting in metastases to the breast with few cases reported in literature.Breast metastases are associated with poor prognosis.The following case highlights the diagnostic challenges associated with metastatic cervical cancer to the breast along with individualized treatment.CASE SUMMARY A 44-year-old G7P5025 with no significant past medical or surgical history presented with heavy vaginal to an outside emergency department where an exam and a pelvic magnetic resonance imaging showed a 4.5 cm heterogenous lobulated cervical mass involving upper two thirds of vagina,parametria and lymph node metastases.Cervical biopsies confirmed high grade adenocarcinoma with mucinous features.A positron emission tomography/computed tomography(PET/CT)did not show evidence of metastatic disease.She received concurrent cisplatin with external beam radiation therapy.Follow up PET/CT scan three months later showed no suspicious fluorodeoxyglucose uptake in the cervix and no evidence of metastatic disease.Patient was lost to follow up for six months.She was re-imaged on re-presentation and found to have widely metastatic disease including breast disease.Breast biopsy confirmed programmed death-ligand 1 positive metastatic cervical cancer.The patient received six cycles of carboplatin and paclitaxel with pembrolizumab.Restaging imaging demonstrated response.Patient continued on pembrolizumab with disease control.CONCLUSION Metastatic cervical cancer to the breast is uncommon with nonspecific clinical findings that can make diagnosis challenging.Clinical history and immunohistochemical evaluation of breast lesion,and comparison to primary tumor can support diagnosis of metastatic cervical cancer to the breast.Overall,the prognosis is poor,but immunotherapy can be considered in select patients and may result in good disease response.

Early adenocarcinoma mixed with a neuroendocrine carcinoma component arising in the gastroesophageal junction: A case report

BACKGROUND Early adenocarcinoma mixed with a neuroendocrine carcinoma(NEC)component arising in the gastroesophageal junctional(GEJ)region is rare and even rarer in young patients.Here,we report such a case in a 29-year-old Chinese man.CASE SUMMARY This patient presented to our hospital with a 3-mo history of dysphagia and regurgitation.Upper endoscopy revealed an elevated nodule in the distal esophagus 1.6 cm above the GEJ line,without Barrett’s esophagus or involvement of the gastric cardia.The nodule was completely resected by endoscopic submu-cosal dissection(ESD).Pathological examination confirmed diagnosis of intra-mucosal adenocarcinoma mixed with an NEC component,measuring 1.5 cm.Immunohistochemically,both adenocarcinoma and NEC components were positive for P53 with a Ki67 index of 90%;NEC was positive for synaptophysin and chromogranin.Next-generation sequencing of 196 genes demonstrated a novel germline mutation of the ERCC3 gene in the DNA repair pathway and a germline mutation of the RNF43 gene,a common gastric cancer driver gene,in addition to pathogenic somatic mutations in P53 and CHEK2 genes.The patient was alive without evidence of the disease 36 mo after ESD.CONCLUSION Early adenocarcinoma with an NEC component arising in the distal esophageal side of the GEJ region showed evidence of gastric origin.

PRaG 3.0 therapy for human epidermal growth factor receptor 2-positive metastatic pancreatic ductal adenocarcinoma:A case report

BACKGROUND Pancreatic ductal adenocarcinoma(PDAC)is a highly fatal disease with limited effective treatment especially after first-line chemotherapy.The human epidermal growth factor receptor 2(HER-2)immunohistochemistry(IHC)positive is associated with more aggressive clinical behavior and shorter overall survival in PDAC.CASE SUMMARY We present a case of multiple metastatic PDAC with IHC mismatch repair proficient but HER-2 IHC weakly positive at diagnosis that didn’t have tumor regression after first-line nab-paclitaxel plus gemcitabine and PD-1 inhibitor treatment.A novel combination therapy PRaG 3.0 of RC48(HER2-antibody-drug conjugate),radio-therapy,PD-1 inhibitor,granulocyte-macrophage colony-stimulating factor and interleukin-2 was then applied as second-line therapy and the patient had confirmed good partial response with progress-free-survival of 6.5 months and overall survival of 14.2 month.She had not developed any grade 2 or above treatment-related adverse events at any point.Percentage of peripheral CD8^(+) Temra and CD4^(+) Temra were increased during first two activation cycles of PRaG 3.0 treatment containing radiotherapy but deceased to the baseline during the maintenance cycles containing no radiotherapy.CONCLUSION PRaG 3.0 might be a novel strategy for HER2-positive metastatic PDAC patients who failed from previous first-line approach and even PD-1 immunotherapy but needs more data in prospective trials.

Radiotherapy for hyoid bone metastasis from lung adenocarcinoma:A case report

BACKGROUND Metastasis to the hyoid bone is an exceptionally rare occurrence,with documented cases limited to breast,liver,colon,skin,lung,and prostate cancers.This report highlights an unusual case involving the metastasis of lung adenocarcinoma to the hyoid bone,accompanied by a distinctive headache.Previous documentation involved surgical resection of the hyoid mass.We present a case displaying the benefits of palliative radiotherapy.CASE SUMMARY A 72-year-old non-smoking,non-alcoholic woman,initially under investigation for a year-long elevation in absolute lymphocyte count,presented with a monthlong history of intermittent throat pain.Despite negative findings in gastroenterological and otolaryngologic examinations,a contrast-enhanced chest computed tomography scan revealed a mediastinal mass and questionable soft tissue thickening in her left anterolateral neck.Subsequent imaging and biopsies confirmed the presence of lung adenocarcinoma metastasis to the hyoid bone.The patient was treated with platinum-based chemo-immunotherapy along with pembrolizumab.Ultimately,the lung cancer was unresponsive.Our patient opted for palliative radiation therapy instead of surgical resection to address her throat pain.As a result,her throat pain was alleviated,and it also incidentally resolved her chronic headaches.This is the second documented case of lung adenocarcinoma metastasizing to the hyoid bone.CONCLUSION Palliative radiotherapy may add to the quality of life in symptomatic patients with cancer metastatic to the hyoid bone.

Computed tomography-based nomogram of Siewert type Ⅱ/Ⅲ adenocarcinoma of esophagogastric junction to predict response to docetaxel, oxaliplatin and S-1

BACKGROUND Neoadjuvant chemotherapy(NAC)has become the standard care for advanced adenocarcinoma of esophagogastric junction(AEG),although a part of the patients cannot benefit from NAC.There are no models based on baseline computed tomography(CT)to predict response of Siewert type II or III AEG to NAC with docetaxel,oxaliplatin and S-1(DOS).AIM To develop a CT-based nomogram to predict response of Siewert type II/III AEG to NAC with DOS.METHODS One hundred and twenty-eight consecutive patients with confirmed Siewert type II/III AEG underwent CT before and after three cycles of NAC with DOS,and were randomly and consecutively assigned to the training cohort(TC)(n=94)and the validation cohort(VC)(n=34).Therapeutic effect was assessed by disease-control rate and progressive disease according to the Response Evaluation Criteria in Solid Tumors(version 1.1)criteria.Possible prognostic factors associated with responses after DOS treatment including Siewert classification,gross tumor volume(GTV),and cT and cN stages were evaluated using pretherapeutic CT data in addition to sex and age.Univariate and multivariate analyses of CT and clinical features in the TC were performed to determine independent factors associated with response to DOS.A nomogram was established based on independent factors to predict the response.The predictive performance of the nomogram was evaluated by Concordance index(C-index),calibration and receiver operating characteristics curve in the TC and VC.RESULTS Univariate analysis showed that Siewert type(52/55 vs 29/39,P=0.005),pretherapeutic cT stage(57/62 vs 24/32,P=0.028),GTV(47.3±27.4 vs 73.2±54.3,P=0.040)were significantly associated with response to DOS in the TC.Multivariate analysis of the TC also showed that the pretherapeutic cT stage,GTV and Siewert type were independent predictive factors related to response to DOS(odds ratio=4.631,1.027 and 7.639,respectively;all P<0.05).The nomogram developed with these independent factors showed an excellent performance to predict response to DOS in the TC and VC(C-index:0.838 and 0.824),with area under the receiver operating characteristic curve of 0.838 and 0.824,respectively.The calibration curves showed that the practical and predicted response to DOS effectively coincided.CONCLUSION A novel nomogram developed with pretherapeutic cT stage,GTV and Siewert type predicted the response of Siewert type II/III AEG to NAC with DOS.

Mixed neuroendocrine and adenocarcinoma of gastrointestinal tract:A complex diagnosis and therapeutic challenge

In this editorial we comment on the manuscript describing a case of adenocarcinoma mixed with a neuroendocrine carcinoma of the gastroesophageal junction.Mixed neuroendocrine and non-neuroendocrine neoplasms of the gastrointestinal system are rare heterogeneous group of tumors characterized by a high malignant potential,rapid growth,and poor prognosis.Due to the rarity of these cancers,the standard therapy is poorly defined.The diagnosis of these tumors is based on combination of morphological features,immunohistochemical and neuroendocrine and epithelial cell markers.Both endocrine and epithelial cell components can act independently of each other and thus,careful grading of each component separately is required.These cancers are aggressive in nature and the potential of each component has paramount importance in the choice of treatment and response.Regardless of the organ of origin,these tumors portend poor prognosis with increased proportion of neuroendocrine component.Multidisciplinary services and strategies are required for the management of these mixed malignancies to provide the best oncological outcomes.The etiopathogenesis of these mixed tumors remains obscure but poses interesting question.We briefly discuss a few salient points in this editorial.

Advanced Lung Adenocarcinoma with EGFR 19-del Mutation Transformed into SCC after EGFR-tyrosine Kinase inhibitors Treatment:A Case report

BACKGROUND Epidermal growth factor receptor tyrosine kinase inhibitors(EGFR-TKIs)significantly improve the survival of patients with Epidermal growth factor receptor(EGFR)sensitive mutations in non-small cell lung cancer(NSCLC).CASE SUMMARY A 67-year-old female patient in advanced lung adenocarcinoma suffered from drug resistance after EGFR-TKIs treatment.Secondary pathological tissue biopsy confirmed squamous cell carcinoma(SCC)transformation.Patients inevitably encountered drug resistance issues after receiving EGFR-TKIs treatment for a certain period of time,while EGFR-TKIs can significantly improve the survival of patients with EGFR-sensitive mutations in NSCLC.Notably,EGFR-TKIs resistance includes primary and acquired.Pathological transformation is one of the mechanisms of acquired resistance in EGFR-TKIs,with SCC transformation being relatively rare.Our results provide more detailed results of the patient’s diagnosis and treatment process on SCC transformation after EGFR-TKIs treatment for lung adenocarcinoma.CONCLUSION Squamous cell carcinoma transformation is one of the acquired resistance mechanisms of EGFR-TKIs in advanced lung adenocarcinoma with EGFR mutations.

Colon Adenocarcinoma in a Retrograde Intussusception: A Case Report and Literature Review

Background: Intussusception is defined as a telescoping of a proximal gastrointestinal segment with its mesentery to a distal one, only 5% occur in adults and in colon the probability that it is caused by a malignant disease is up to 65%. Only 1% occurs in a retrograde manner, the rest occur in an anterograde manner. Aim: Describe the clinical presentation of an intussusception in the adult patient as well as its most frequent causes and possible complications that influence decision making for a definitive treatment. Case Presentation: A 66-year-old woman diagnosed with colon adenocarcinoma who underwent elective transverse colectomy and colonic anastomosis with an incidental finding of a transverse colon tumor in a retrograde intussusception was studied. Conclusion: In any adult patient with an intussusception especially in colon a neoplasia should be suspected and the affected segment should be resected without being reduced due to the risk of perforation and tumor dissemination.

Pancreatic panniculitis as the first presentation of pancreatic ductaladenocarcinoma

To the Editor:Pancreatic panniculitis,also known as pancreatic fat necrosis or enzymatic panniculitis,is a rare type of panniculitis that occurs in 0.3%−3%of patients with pancreatic disease such as acute or chronic pancreatitis and pancreatic carcinoma,especially acinar cell carcinoma[1,2].The clinical manifestations are nonspecific erythema tender nodules.

Lung adenocarcinoma with initial binocular symptoms

Dear Editor,Lung adenocarcinoma with choroidal metastasis is a common form of cancer,with breast cancer accounting for 40%-53%and lung cancer accounting for 20%-29%of primary cases with choroidal metastases[1].This type of metastatic cancer typically affects people aged 40-70y,and is more prevalent in women than men[1].Ocular symptoms,including vision loss,can be an early indication of the disease,as many tumors are asymptomatic in their early stages.Studies have shown that 40.3%of cases involve the macular region,which explains why ocular symptoms are often the first manifestation of the disease[2].When choroidal metastasis is suspected in patients without a history of cancer,a combination of diagnostic tools should be used to identify the primary source of the tumor.Choroidal tumors can serve as an indication of future lung cancer diagnosis in some patients with lung cancer[1].In this report,we present a case of bilateral lung adenocarcinoma where ocular symptoms were the first indication of the disease.

miR-125b reverses cisplatin resistance by regulating autophagy via targeting RORA/BNIP3L axis in lung adenocarcinoma

The platinum-based chemotherapy is one of the most frequently used treatment protocols for lung adenocarcinoma(LUAD),and chemoresistance,however,usually results in treatment failure and limits its application in the clinic.It has been shown that microRNAs(miRNAs)play a significant role in tumor chemoresistance.In this study,miR-125b was identified as a specific cisplatin(DDP)-resistant gene in LUAD,as indicated by the bioinformatics analysis and the real-time quantitative PCR assay.The decreased serum level of miR-125b in LUAD patients was correlated with the poor treatment response rate and short survival time.MiR-125b decreased the A549/DDP proliferation,and the multiple drug resistance-and autophagy-related protein expression levels,which were all reversed by the inhibition of miR-125b.In addition,xenografts of human tumors in nude mice were suppressed by miR-125b,demonstrating that through autophagy regulation,miR-125b could reverse the DDP resistance in LUAD cells,both in vitro and in vivo.Further mechanistic studies indicated that miR-125b directly repressed the expression levels of RORA and its downstream BNIP3L,which in turn inhibited autophagy and reversed chemoresistance.Based on these findings,miR-125b in combination with DDP might be an effective treatment option to overcome DDP resistance in LUAD.

Effects of neoadjuvant chemotherapy vs chemoradiotherapy in the treatment of esophageal adenocarcinoma:A systematic review and meta-analysis

BACKGROUND Neoadjuvant therapy is an essential modality for reducing the clinical stage of esophageal cancer;however,the superiority of neoadjuvant chemotherapy(nCT)or neoadjuvant chemoradiotherapy(nCRT)is unclear.Therefore,a discussion of these two modalities is necessary.AIM To investigate the benefits and complications of neoadjuvant modalities.METHODS To address this concern,predefined criteria were established using the PICO protocol.Two independent authors performed comprehensive searches using predetermined keywords.Statistical analyses were performed to identify significant differences between groups.Potential publication bias was visualized using funnel plots.The quality of the data was evaluated using the Risk of Bias Tool 2(RoB2)and the GRADE approach.RESULTS Ten articles,including 1928 patients,were included for the analysis.Significant difference was detected in pathological complete response(pCR)[P<0.001;odds ratio(OR):0.27;95%CI:0.16-0.46],30-d mortality(P=0.015;OR:0.4;95%CI:0.22-0.71)favoring the nCRT,and renal failure(P=0.039;OR:1.04;95%CI:0.66-1.64)favoring the nCT.No significant differences were observed in terms of survival,local or distal recurrence,or other clinical or surgical complications.The result of RoB2 was moderate,and that of the GRADE approach was low or very low in almost all cases.CONCLUSION Although nCRT may have a higher pCR rate,it does not translate to greater long-term survival.Moreover,nCRT is associated with higher 30-d mortality,although the specific cause for postoperative complications could not be identified.In the case of nCT,toxic side effects are suspected,which can reduce the quality of life.Given the quality of available studies,further randomized trials are required.

Epidemiology of EGFR Mutation in Adenocarcinoma NSCLC Patients in India: A Systematic Review and Meta-Analysis

Studies reporting the Indian prevalence of Epidermal Growth Factor Receptor (EGFR) mutation are mostly single centers with small sample sizes. This systematic review and meta-analysis summarized the available evidence of EGFR mutation epidemiology in Indian patients with adenocarcinoma (ADC) Non-Small Cell Lung Cancer (NSCLC). We conducted a structured literature search in PubMed, and EMBASE databases from January 2004 through October 2019. The primary outcome of interest was prevalence of EGFR mutation by gender, smoking status, and mutation subtype. The review included 34 studies. EGFR mutation prevalence was 39.5% in patients with ADC, and significantly higher in females, non-smokers, and patients with exon 19 deletions. The EGFR mutation frequency in Indian patients with ADC was higher than reported in Caucasians but at a lower range of that reported in East Asians. These findings support the use of EGFR mutation testing to guide choice of treatment.