Implementation of a High-Accuracy Targeted Gene Expression Panel for Clinical Care.

This study describes the validation of a clinical RNA expression panel with evaluation of concordance between gene copy gain by a next-generation sequencing (NGS) assay and high gene expression by an RNA expression panel. The RNA Salah Targeted Expression Panel (RNA STEP) was designed with input from oncologists to include 204 genes with utility for clinical trial prescreening and therapy selection. RNA STEP was validated with the nanoString platform using remnant formalin-fixed, paraffin-embedded-derived RNA from 102 patients previously tested with a validated clinical NGS panel. The repeatability, reproducibility, and concordance of RNA STEP results with NGS results were evaluated. RNA STEP demonstrated high repeatability and reproducibility, with excellent correlation (r > 0.97, P < 0.0001) for all comparisons. Comparison of RNA STEP high gene expression (log2 ratio ≥ 2) versus NGS DNA-based gene copy number gain (copies ≥ 5) for 38 mutually covered genes revealed an accuracy of 93.0% with a positive percentage agreement of 69.4% and negative percentage agreement of 93.8%. Moderate correlation was observed between platforms (r = 0.53, P < 0.0001). Concordance between high gene expression and gene copy number gain varied by specific gene, and some genes had higher accuracy between assays. Clinical implementation of RNA STEP provides gene expression data complementary to NGS and offers a tool for prescreening patients for clinical trials.

Microcomputed tomography as a diagnostic tool for detection of lymph node metastasis in non-small cell lung cancer: A decision-support approach for pathological examination "A pilot study for method validation".

Background: Non-small cell lung cancer (NSCLC) patients without lymph node (LN) metastases (pN0) may exhibit different survival rates, even when their T stage is similar. This divergence could be attributed to the current pathology practice, wherein LNs are examined solely in two-dimensional (2D). Unfortunately, adhering to the protocols of 2D pathological examination does not ensure the exhaustive sampling of all excised LNs, thereby leaving room for undetected metastatic foci in the unexplored depths of tissues. The employment of micro-computed tomography (micro-CT) facilitates a three-dimensional (3D) evaluation of all LNs without compromising sample integrity. In our study, we utilized quantitative micro-CT parameters to appraise the metastatic status of formalin-fixed paraffin-embedded (FFPE) LNs. Methods: Micro-CT scans were conducted on 12 FFPEs obtained from 8 NSCLC patients with histologically confirmed mediastinal LN metastases. Simultaneously, whole-slide images from these FFPEs underwent scanning, and 47 regions of interest (ROIs) (17 metastatic foci, 11 normal lymphoid tissues, 10 adipose tissues, and 9 anthracofibrosis) were marked on scanned images. Quantitative structural variables obtained via micro-CT analysis from tumoral and non-tumoral ROIs, were analyzed. Result: Significant distinctions were observed in linear density, connectivity, connectivity density, and closed porosity between tumoral and non-tumoral ROIs, as indicated by kappa coefficients of 1, 0.90, 1, and 1, respectively. Receiver operating characteristic analysis substantiated the differentiation between tumoral and non-tumoral ROIs based on thickness, linear density, connectivity, connectivity density, and the percentage of closed porosity. Conclusions: Quantitative micro-CT parameters demonstrate the ability to distinguish between tumoral and non-tumoral regions of LNs in FFPEs. The discriminatory characteristics of these quantitative micro-CT parameters imply their potential usefulness in developing an artificial intelligence algorithm specifically designed for the 3D identification of LN metastases while preserving the FFPE tissue.

Oncological results in primary and secondary malignant chest wall tumors.

Background: This study aims to evaluate the oncological results of primary and secondary chest wall tumors treated with curative resections and to investigate possible prognostic factors. Methods: Between January 2010 and December 2021, a total of 77 patients (53 males, 24 females; median age: 59 years; range, 3 to 87 years) who underwent curative resection for malignant chest wall tumors were retrospectively analyzed. Each tumor was staged according to its histological type. Age, sex, tumor diameter, tumor type (primary/secondary), histological tumor type, grade, stage, complete resection, rib resection, reconstruction, neoadjuvant and adjuvant therapy, recurrence, and survival data were recorded. Results: Of the chest wall tumors, 33 (42.9%) were primary and 44 (57.1%) were secondary (local invasion, metastasis). Nine (11.7%) patients had positive surgical margins. Chest wall resection was most commonly performed due to lung cancer invasion (46.8%), followed by Ewing sarcoma (13%). Recurrence was observed in 34 (44.2%) patients. The five-year recurrence-free survival rate was 42.7% and the five-year overall survival rate was 58.6%. There was no significant difference between the primary and secondary tumors in terms of recurrence-free and overall survival (p=0.663 and p=0.313, respectively). In the multivariate analysis, tumor grade and rib resection were found to be independent prognostic factors for both recurrence-free survival (p=0.005 and p<0.001, respectively) and overall survival (p=0.048 and p=0.007, respectively). Conclusion: Successful oncological results can be achieved in wellselected patients with primary and secondary chest wall tumors. The grade of the tumor should be taken into account while determining the neoadjuvant or adjuvant treatment approach and surgical margin width. Rib resection should not be avoided when necessary.

Primary epithelioid angiosarcoma of endometrium.

Angiosarcoma is a poor prognostic tumor observed less than 1% in soft tissue, while it is rarely detected in the endometrium and has been described in few case reports. In this report, we present a case of primary epithelioid angiosarcoma of endometrium to raise awareness and emphasize for pathologists and clinicians.

Three in one: A case presented with multiloculated thymic cyst, thymic Hodgkin lymphoma and pericardial cyst.

Multiloculated thymic cyst is a cystic reaction of medullary epithelium to inflammatory process. In most cases, the exact cause of the inflammation is not known. Hodgkin lymphoma and multiloculated thymic cyst coexistence is a rare condition and may cause significant diagnostic difficulties. Herein, we present a rare case who underwent surgery for multiloculated thymic cyst and was subsequently diagnosed with Hodgkin lymphoma and had a concurrent pericardial cyst.

A phase I/IB trial of binimetinib in combination with erlotinib in NSCLC harboring activating KRAS or EGFR mutations.

BACKGROUND: Activating mutations in EGFR or KRAS are highly prevalent in NSCLC, share activation of the MAPK pathway and may be amenable to combination therapy to prevent negative feedback activation. METHODS: In this phase 1/1B trial, we tested the combination of binimetinib and erlotinib in patients with advanced NSCLC with at least 1 prior line of treatment (unless with activating EGFR mutation which could be treatment-naïve). A subsequent phase 1B expansion accrued patients with either EGFR- or KRAS-mutation using the recommended phase 2 dose (RP2D) from Phase 1. The primary objective was to evaluate the safety of binimetinib plus erlotinib and establish the RP2D. RESULTS: 43 patients enrolled (dose-escalation = 23; expansion = 20). 17 harbored EGFR mutation and 22 had KRAS mutation. The RP2D was erlotinib 100 mg daily and binimetinib 15 mg BID × 5 days/week. Common AEs across all doses included diarrhea (69.8%), rash (44.2%), fatigue (32.6%), and nausea (32.6%), and were primarily grade 1/2. Among KRAS mutant patients, 1 (5%) had confirmed partial response and 8 (36%) achieved stable disease as best overall response. Among EGFR mutant patients, 9 were TKI-naïve with 8 (89%) having partial response, and 8 were TKI-pretreated with no partial responses and 1 (13%) stable disease as best overall response. CONCLUSIONS: Binimetinib plus erlotinib demonstrated a manageable safety profile and modest efficacy including one confirmed objective response in a KRAS mutant patient. While clinical utility of this specific combination was limited, these results support development of combinations using novel small molecule inhibitors of RAS, selective EGFR- and other MAPK pathway inhibitors, many of which have improved therapeutic indices. CLINICAL TRIAL REGISTRATION: NCT01859026.

Comparison of the effect of the autogenic and xenogenic use of platelet-rich plasma on rabbit chondrocutaneous composite graft survival.

The platelet-rich plasma (PRP) has become popular in the medical world due to its content of growth factors and numerous studies are experimental. In experimental studies, the preparation and application of PRP are problematic and allogenic PRP transfers have been preffered, because of the difficulties in preparation of autogenic PRP in animal experiments. Xenogenic transfers and their effects have not been studied in this topic. This study aimed to investigate the effect of autogenic and xenogenic use of PRP on composite graft viability.Methods: Two composite grafts are prepared for each ear of nine rabbits. Each ear was randomly divided into three groups. After the procedure, the wound edges and base were injected with 1 cc serum physiologic, autogenic PRP or 1 cc human-derived xenogenic PRP. At 3 weeks, samples were taken, photographic and histopathological evaluations were made.Results: The graft viability was better in autogenic and xenogenic group compared to the control group. In comprasion of autogenic and xenogenic groups, although the macroscopic evaluation revealed better graft viability and less necrosis in the group which had been treated with autogenic PRP, the difference was not statistically significant. The three groups did not significantly differ in terms of inflammation. Vascularization examined histopathologically. CD31 staining, which was used to evaluate angiogenesis, was significantly higher in the autogenic PRP group than the remaining two groups.Conclusion: Although autogenic PRP has better results histopathologically, the xenogenic use of PRP may be an alternative for studies, when macroscopic evaluation is necessary.

The relationship between clinicopathological parameters and PD-L1 expression level in advanced stage non-small cell lung cancer.

Introduction: Clinicopathological parameters related to programmed death ligand 1 (PD-L1) expression levels have been investigated in several studies. However, the results of these studies are conflicting and vary in different populations. This study aimed to investigate the relation of clinicopathological parameters with PD-L1 expression level in advanced stage non-small cell lung cancer patients. Materials and Methods: The patients diagnosed with non-small cell lung cancer were enrolled, retrospectively. The data of clinicopathological parameters was collected. Clinicopathological parameters in relation to PD-L1 expression levels (0%, 1-50%, and >50%) were analyzed as univariable and multivariable. Result: In total, 384 patients were enrolled. PD-L1 expression in tumor cells was between 1-50%, and >50% in 41.4%, and 23.4% of patients, respectively. There was no PD-L1 expression in 35.2% of the patients. In univariable analysis, we found that the parameters associated with PD-L1 expression levels revealed that metastatic site number, the subtype of cancer, diagnostic material type, platelet number, and LDH level were statistically significant. Adenocarcinoma frequency was higher in tumors that had PD-L1 expression >50% than in tumors that did not express PD-L1 and the difference was statistically significant (p= 0.04, coefficient= 0.3, 95% CI 0.09-0.94). Cytology as diagnostic material was significant in PD-L1 level 1-50% comparing to >50% (p= 0.02, coefficient= 2.2, 95% CI= 1.08-4.46). Conclusions: According to the results of our study, many of the clinicopathological parameters are not related to the PD-L1 level. The histological subtype and diagnostic material may affect the level of PD-L1 expression.

Evaluation of lung cancer biomarkers profile for the decision of targeted therapy in EBUS-TBNA cytological samples.

BACKGROUND: Guidelines recommend performing biomarker tests for epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), BRAF and ROS proto-oncogene-1(ROS1) genes and protein expression of programmed death ligand-1(PD-L1) in patients with non-small lung cell carcinoma (NSCLC). Studies reported that endobronchial ultrasound-transbronchial needle aspiration (EBUS-TBNA) can provide sufficient material for cancer biomarker analyses, but there are still concerns about the subject. AIM: The purpose of the study was to assess the adequacy of EBUS-TBNA for testing lung cancer biomarkers. METHODS: We retrospectively reviewed patients with NSCLC whose EBUS-TBNA was analysed for EGFR, ALK, ROS-1, BRAF and PD-L1 expression between December 2011 and December 2020. RESULTS: A total of 394 patients were enrolled in the study. EGFR mutation and ALK fusion were the most common studied biomarkers. EBUS-TBNA adequacy rate for biomarker tests was found 99.0% for EGFR, 99.1 for ALK, 97.2% for ROS1, 100% for BRAF and 99.3% for PD-L1 testing. Multivariate analysis revealed the histological type, history of treatment for NSCL, size, or 18-fluorodeoxyglucose uptake of sampled lesion did not show any association with TBNA adequacy for biomarker testing. CONCLUSION: EBUS-TBNA can provide adequate material for biomarker testing for EGFR, ALK, ROS-1, BRAF and PD-L1 expression.

A CT-Based Radiomic Signature for the Differentiation of Pulmonary Hamartomas from Carcinoid Tumors.

Radiomics is a new image processing technology developed in recent years. In this study, CT radiomic features are evaluated to differentiate pulmonary hamartomas (PHs) from pulmonary carcinoid tumors (PCTs). A total of 138 patients (78 PCTs and 60 PHs) were evaluated. The Radcloud platform (Huiying Medical Technology Co., Ltd., Beijing, China) was used for managing the data, clinical data, and subsequent radiomics analysis. Two hand-crafted radiomics models are prepared in this study: the first model includes the data regarding all of the patients to differentiate between the groups; the second model includes 78 PCTs and 38 PHs without signs of fat tissue. The separation of the training and validation datasets was performed randomly using an (8:2) ratio and 620 random seeds. The results revealed that the MLP method (RF) was best for PH (AUC = 0.999) and PCT (AUC = 0.999) for the first model (AUC = 0.836), and PC (AUC = 0.836) in the test set for the second model. Radiomics tumor features derived from CT images are useful to differentiate the carcinoid tumors from hamartomas with high accuracy. Radiomics features may be used to differentiate PHs from PCTs with high levels of accuracy, even without the presence of fat on the CT. Advances in knowledge: CT-based radiomic holds great promise for a more accurate preoperative diagnosis of solitary pulmonary nodules (SPNs).

HER2 Amplification by Next-Generation Sequencing in Lung Carcinoma: A Comparison of NGS Amplified and Non-amplified Cases by Immunohistochemistry and In Situ Hybridization

Background: Although the role of HER2 amplification and its evaluation methods are well known in breast carcinoma, methods for detection of HER2 amplification in non-small cell lung carcinoma are unclear. Next-generation sequencing is widely used in searching multiple therapeutic targets, and it is possible to evaluate copy number variation of genes by next-generation sequencing. Aims: To re-evaluate the HER2 status of non-small cell lung carcinoma cases detected as HER2 amplified and non-amplified by next-generation sequencing via the most commonly used HER2 investigation methods in routine pathology practice, namely immunohistochemistry and in situ hybridization. Study Design: Retrospective cross-sectional study. Methods: Among the 256 patients whose mutation profiles were examined by next-generation sequencing, HER2 amplified (13 cases) and non-HER2-amplified (13 cases) were determined as study and control groups, respectively, by next-generation sequencing. HER2 next-generation sequencing amplified tumors were investigated for HER2 expression and amplification using immunohistochemistry and silver in situ hybridization. Results: From a group of 256 non-small cell lung carcinoma, 33 tumors (12.8%) showed HER2 amplification with next-generation sequencing. Although we observed more frequent HER2 positivity by immunohistochemistry in next-generation sequencing-amplified cases, when compared to non-amplified cases (50% and 23% respectively), the difference was not significant (P = .221). Within the HER2 amplified group, inter-method-agreement was very good between next-generation sequencing results amplification and in situ hybridization status. Next-generation sequencing results showed a strong interclass correlation coefficient with HER2/cell (P = .009, r = 0.777) and HER2/CEP17 ratio (P = .001, r = 0.805). The median HER2/CEP17 ratio was higher in the next-generation sequencing amplified group (P = .013); however, three cases were found to be amplified by silver in situ hybridization among the next-generation sequencing non-amplified cases. EGFR and FGFR1 amplification were more frequent in HER2 next-generation sequencing amplified group than next-generation sequencing non-amplified group (P < .001). Conclusion: Until the effects of HER2 amplification on the HER2 protein are well understood and pulmonary carcinoma algorithms are defined, non-small cell lung carcinomas found to be amplified by next-generation sequencing should be verified by additional methods.

Role of PD-1/PD-L1-mediated tumour immune escape mechanism and microsatellite instability in the BCG failure of high-grade urothelial carcinomas.

BACKGROUND: Intravesical BCG treatment fails inexplicably in 30%-45% of patients for high-grade nonmuscle-invasive bladder cancer (NMIBC). We aimed to investigate the role of PD-1/PD-L1 interaction on BCG failure of high-grade NMIBC and to identify biomarkers for predicting BCG responsive cases. METHODS: Thirty BCG responsive and 29 nonresponsive NMIBCs were included in the study. Expressions of PDL1(SP-263), MSH2, MSH6, PMS2, and MLH1 were evaluated on pre- and post-BCG transurethral resection (TUR-B) specimens by immunohistochemistry. PD-L1(SP-263) expression was categorised as negative/low, high. DNA mismatch repair protein (MMR) expressions were classified as "reduced" if ≤30% of nuclei stained, "preserved" if >30% of nuclei stained. Microsatellite instability (MSI) testing was performed by PCR using five mononucleotide markers. RESULTS: Reduced DNA MMR protein expression was found to be significantly higher in the pretreatment biopsies of BCG-responsive group than the BCG nonresponsive tumour group (p = 0.022). PD-L1 expression did not show any significant difference between the pre- and posttreatment TUR-B specimens of the BCG nonresponsive tumour group or between the pretreatment TUR-B specimens of BCG nonresponsive and the BCG responsive groups (p = 0.508, p = 0.708, respectively). DISCUSSION: Immune escape of tumour cells by PD-1/PD-L1 interaction does not seem to have any role in BCG failure of NMIBCs. Reduced MMR expression may help to determine cases that will respond well to BCG therapy. A better antitumour activity of BCG in NMIBCs with reduced MMR expression may be related to the ongoing accumulation of cancer neoantigens in correlation with increased tumour mutation load as a result of DNA repair defects.

CT imaging-based machine learning model: a potential modality for predicting low-risk and high-risk groups of thymoma: "Impact of surgical modality choice".

INTRODUCTION: Radiomics methods are used to analyze various medical images, including computed tomography (CT), magnetic resonance, and positron emission tomography to provide information regarding the diagnosis, patient outcome, tumor phenotype, and the gene-protein signatures of various diseases. In low-risk group, complete surgical resection is typically sufficient, whereas in high-risk thymoma, adjuvant therapy is usually required. Therefore, it is important to distinguish between both. This study evaluated the CT radiomics features of thymomas to discriminate between low- and high-risk thymoma groups. MATERIALS AND METHODS: In total, 83 patients with thymoma were included in this study between 2004 and 2019. We used the Radcloud platform (Huiying Medical Technology Co., Ltd.) to manage the imaging and clinical data and perform the radiomics statistical analysis. The training and validation datasets were separated by a random method with a ratio of 2:8 and 502 random seeds. The histopathological diagnosis was noted from the pathology report. RESULTS: Four machine-learning radiomics features were identified to differentiate a low-risk thymoma group from a high-risk thymoma group. The radiomics feature names were Energy, Zone Entropy, Long Run Low Gray Level Emphasis, and Large Dependence Low Gray Level Emphasis. CONCLUSIONS: The results demonstrated that a machine-learning model and a multilayer perceptron classifier analysis can be used on CT images to predict low- and high-risk thymomas. This combination could be a useful preoperative method to determine the surgical approach for thymoma.

COVID-19 Treatment at a Glance.

As coronavirus disease 2019 (COVID-19) spreads across the world, the ongoing clinical trials are leading to a big race worldwide to develop a treatment that will help control the pandemic. Unfortunately, COVID-19 does not have any known effective treatment with reliable study results yet. In this pandemic, there is not a lot of time to develop a new specific agent because of the rapid spread of the disease. The process of developing a vaccine is long and requires hard work. Although the pathophysiology of the disease is not fully understood, some of the proposed treatment alternatives are based on old evidence and some have been used with the idea that they might work owing to their mechanism of action. The efficacy, reliability, and safety of the currently available treatment alternatives are therefore a matter of debate. Currently, the main therapies used in the treatment of COVID-19 are antiviral drugs and chloroquine/hydroxychloroquine. Other proposed options include tocilizumab, convalescent plasma, and steroids, but the mainstay of the treatment in intensive care units remains supportive therapies.

Unclear Issues Regarding COVID-19.

Scientists from all over the world have been intensively working to discover different aspects of Coronavirus disease 2019 (COVID-19) since the first cluster of cases was reported in China. Herein, we aimed to investigate unclear issues related to transmission and pathogenesis of disease as well as accuracy of diagnostic tests and treatment modalities. A literature search on PubMed, Ovid, and EMBASE databases was conducted, and articles pertinent to identified search terms were extracted. A snow-ball search strategy was followed in order to retrieve additional relevant articles. It was reported that viral spread may occur during the asymptomatic phase of infection, and viral load was suggested to be a useful marker to assess disease severity. In contrast to immune response against viral infections, cytotoxic T lymphocytes decline in SARS-CoV-2 infection, which can be partially explained by direct invasion of T lymphocytes or apoptosis activated by SARS-CoV-2. Dysregulation of the urokinase pathway, cleavage of the SARS-CoV-2 Spike protein by FXa and FIIa, and consumption coagulopathy were the proposed mechanisms of the coagulation dysfunction in COVID-19. False-negative rates of reverse transcriptase polymerase chain reaction varied between 3% and 41% across studies. The probability of the positive test was proposed to decrease with the number of days past from symptom onset. Safety issues related to infection spread limit the use of high flow nasal oxygen (HFNO) and continuous positive airway pressure (CPAP) in hypoxic patients. Further studies are required to elucidate the challenging issues, thus enhancing the management of COVID-19 patients.

What We Learned about COVID-19 So Far? Notes from Underground.

The novel coronavirus pandemic poses a major global threat to public health. Our knowledge concerning every aspect of COVID-19 is evolving rapidly, given the increasing data from all over the world. In this narrative review, the Turkish Thoracic Society Early Career Taskforce members aimed to provide a summary on recent literature regarding epidemiology, clinical findings, diagnosis, treatment, prevention, and control of COVID-19. Studies revealed that the genetic sequence of the novel coronavirus showed significant identity to SARS-CoV and MERS-CoV. Angiotensin-converting enzyme 2 receptor is an important target of the SARS-CoV-2 while entering an organism. Smokers were more likely to develop the disease and have a higher risk for ICU admission. The mean incubation period was 6.4 days, whereas asymptomatic transmission was reported up to 25 days after infection. Fever and cough were the most common symptoms, and cardiovascular diseases and hypertension were reported to be the most common comorbidities among patients. Clinical manifestations range from asymptomatic and mild disease to severe acute respiratory distress syndrome. Several patients showed typical symptoms and radiological changes with negative RT-PCR but positive IgG and IgM antibodies. Although radiological findings may vary, bilateral, peripherally distributed, ground-glass opacities were typical of COVID-19. Poor prognosis was associated with older age, higher Sequential Organ Failure Assessment score, and high D-dimer level. Chloroquine was found to be effective in reducing viral replication in vitro. Likewise, protease inhibitors, including lopinavir/ritonavir, favipiravir, and nucleoside analogue remdesivir were proposed to be the potential drug candidates in COVID-19 management. Despite these efforts, we still have much to learn regarding the transmission, treatment, and prevention of COVID-19.

Duodenal bulb biopsy in the diagnostic work-up of coeliac disease.

Coeliac disease (CD) is an autoimmune enteropathy which can present with patchy mucosal lesions. The aim of the present study is to investigate the significance of duodenal bulb biopsy in the diagnostic work-up of CD in both pediatric and adult patients, and to highlight the key points for pathologists. D1 (duodenal bulb) and D2 (distal duodenum) biopsies of 153 newly diagnosed serology-positive CD patients were evaluated for villous/crypt ratio and intraepithelial lymphocyte (IEL) counts on CD3-stained slides and were classified according to Marsh. Mucosal pathology was patchy in 15% (13% only D1 and 2% only D2) of patients, and 85% of patients had diffuse mucosal pathology involving both D1 and D2 biopsies which showed concordant histology in 60% and discordant in 25% of the cases. Though majority of the patients (75%) with only D1 involvement were pediatric cases, no significant difference was found between pediatric and adult patients when all cases were considered (17 vs 14%). Our results clearly indicate that without D1 sampling, diagnosis of CD would have been missed in a significant number of cases (13%), thereby highlighting the importance of taking duodenal biopsies from multiple sites in the diagnostic work-up of CD. We, therefore, conclude that every biopsy piece from both D1 and D2 should be carefully evaluated for the whole spectrum of mucosal changes caused by gluten ingestion and classified using a scheme based on Marsh to allow recognition of mild lesions.

Evaluation of epidermal growth factor receptor mutations and thyroid transcription factor-1 status in Turkish non-small cell lung carcinoma patients: A study of 600 cases from a single center.

BACKGROUND: This study aims to investigate the frequency, distribution, and morphological/immunohistochemical features of epidermal growth factor receptor mutations and to examine the possible relationship between the material type and technical success of mutation analysis in Turkish population with non-small cell lung cancer. METHODS: Between September 2012 and December 2015, a total of 499 consecutive, treatment-naïve patients (437 males, 163 females; mean age 61 years; range, 30 to 84 years) with primary or metastatic non-small cell lung cancer who underwent epidermal growth factor receptor mutation testing using Sanger sequencing method were retrospectively analyzed. Archival records and hematoxylin-eosine and immunohistochemically stained sections were re-examined. The thyroid transcription factor-1 and napsin A immunohistochemical stains were performed on tissue array blocks. RESULTS: Seventy-five mutations were detected in 70 patients (14%). The success rate of testing and intact deoxyribonucleic acid fragment length were significantly higher in the cytological material, compared to tissue specimens (p<0.001). The mutation rate in adenocarcinomas was 33.9% for women and 9.4% for men. The most common mutation was L746-E750del in exon 19 (29.3%), followed by the L858R mutation in exon 21 (28%). The mutation rate was the highest in micropapillary (40%) and lowest in solid (5.4%) adenocarcinomas. All epidermal growth factor receptor mutations, except for one, were positive for the thyroid transcription factor-1. The single nucleotide polymorphism Q787Q in exon 20 was observed in 79.6% of patients. CONCLUSION: The frequency and distribution of epidermal growth factor receptor mutations in the Turkish patients with non-small cell lung cancer are similar to the European populations. These results also demonstrate that cytological materials are highly reliable for epidermal growth factor receptor mutation testing, and the probability of detection of wild-type epidermal growth factor receptor is low in cases of thyroid transcription factor-1 negativity.