Clinical characteristics and treatment outcomes of Asian patients with T-cell large granular lymphocytic Leukemia: a single-center analysis of 67 cases.

Large granular lymphocytic (LGL) leukemia is a clonal lymphoproliferative disorder of LGLs derived from cytotoxic T lymphocytes or natural killer cells. However, the clinical features and treatment responses are still not fully understood because of the rarity of the disease. To describe and assess a cohort of patients with T-cell large granular lymphocytic leukemia (T-LGLL). Single-center, retrospective, observational study. We retrospectively collected the clinical data of patients diagnosed with T-LGLL at Seoul National University Hospital since 2006. We included 67 patients in this study. The median age at diagnosis was 60 years. Additionally, 37 patients (55%) were symptomatic, and 25 (37%) had splenomegaly; 54 patients (81%) required treatment. Cyclophosphamide (n = 35), methotrexate (n = 25), and cyclosporin A (n = 19) were used most frequently for treatment, and their overall response rates were similar: cyclophosphamide (77%), methotrexate (64%), and cyclosporin A (63%). Splenomegaly was associated with an increased response rate to first-line therapy and a decreased complete response rate. Thrombocytopenia was associated with decreased response rates to cyclophosphamide, methotrexate, cyclosporin A, and steroids. In contrast, a high LGL number (> 2000/µL) in the peripheral blood smear was associated with increased response rates to cyclophosphamide, methotrexate, cyclosporin A, and steroids. This study describes the clinical features and treatment outcomes of patients with T-LGLL, providing valuable information for clinical decision-making regarding T-LGLL treatment.

Establishing Conditions for Blood Smear Drying and Staining on Sysmex SP-50 for Leukocyte Differential Count.

BACKGROUND: The purpose of this study was to determine the staining conditions and appropriate fan1 start time (FAN1ST) for Sysmex SP-50 to produce blood smears (BS) that reflect the true lymphocyte morphology of patient samples. METHODS: Using different start times of fan1, we obtained a set of 84 blood smear slides from 21 blood samples and measured 10,920 lymphocyte areas, which were then converted to compare lymphocyte sizes. We also performed a leukocyte differential count using Sysmex DI-60 on 202 blood smear slides prepared before and after the change in staining conditions and compared the results. RESULTS: The mean lymphocyte sizes at FAN1ST 0 second, 5 seconds, 10 seconds, and 30 seconds were 12.55 µm, 12.14 µm, 11.27 µm, and 10.50 µm, respectively. The mean differences in the preclassification of neutrophils, lymphocytes, monocytes, eosinophils, and basophils in DI-60, according to the SP-50 staining conditions, were 0.88, -1.58, -0.24, 0.37, and 0.07, respectively. CONCLUSIONS: Wright-Giemsa staining of blood smears prepared on the SP-50 showed that changing the pH of the concentrated phosphate buffer to 6.6 and adjusting the staining time did not affect the results of the leukocyte differential count. However, since fan1 was used to dry the blood smear on the SP-50 and the lymphocyte size gradually decreased as the start time was delayed, it was necessary to set a start time for fan1 that did not affect the lymphocyte size.

Laboratory Perspective of Concurrent Acute Myeloid Leukemia and COVID-19: a Case Report and Review of Literature.

BACKGROUND: Whether the diagnosis and treatment of coronavirus disease 2019 (COVID-19) affect the clinical course of patients with hematologic malignancies has been of interest during the COVID-19 pandemic. METHODS: We describe a 47-year-old female who was concurrently diagnosed with COVID-19 and acute myeloid leukemia (AML). RESULTS: She developed COVID-19 pneumonia which required treatment with remdesivir and dexamethasone, and induction therapy for t-AML was delayed. After her COVID-19 was resolved and isolation ended, follow-up bone marrow examination showed decreased leukemic burden. CONCLUSIONS: This case describes possible effects of COVID-19 treatment on the clinical course of patients with AML from a laboratory perspective.

Hemophagocytic lymphohistiocytosis associated with parvovirus B19-induced aplastic crisis in a hereditary spherocytosis patient: A case report and literature review.

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of pathologic immune activation. It occurs because of severe inflammation due to uncontrolled proliferation of activated lymphocytes and histiocytes, characterized by the production of excessive levels of cytokines. Virus-associated HLH is a well-known entity, and parvovirus B19 is one of the common causes. Parvovirus B19 can also affect blood cell lineages. Therefore, HLH may be accompanied by several diseases such as cytopenia, aplastic anemia, and myelodysplastic syndrome. Herein, we report the case of a patient with hereditary spherocytosis who was diagnosed with parvovirus B19-induced HLH and aplastic crisis. A 7-year-old girl presented to our hospital with fever, pleural effusion, pancytopenia, hepatosplenomegaly, and hypotension. A bone marrow biopsy was performed under the suspicion of HLH, which revealed hemophagocytes. The diagnostic criteria for HLH were met, and prompt chemoimmunotherapy was initiated considering the clinically unstable situation. Her health improved rapidly after initiating treatment. Further study revealed that she had hereditary spherocytosis, and parvovirus B19 had caused aplastic crisis and HLH. The patient's clinical progress was excellent, and chemoimmunotherapy was reduced and discontinued at an early stage. This case shows that aplastic crisis and HLH can coexist with parvovirus B19 infection in patients with hereditary spherocytosis. Although the prognosis was good in this case of HLH caused by parvovirus B19, early detection and active treatment are essential.

Detection of Methylated SEPT9 in Korean Colorectal Cancer Patients: Comparison with Previous Studies.

BACKGROUND: This study aimed to investigate the detection of methylated Septin 9 (mSEPT9) in Korean patients with colorectal cancer (CRC) and compare the results with those of previous studies. METHODS: A total of 127 plasma samples (111 patients with untreated CRC, 5 patients with adenomas, and 11 CRC patients treated with concurrent chemoradiotherapy before surgery) were collected. mSEPT9 was measured qualitatively with the Abbott RealTime ms9 Colorectal Cancer Assay. RESULTS: mSEPT9 was detected in 44 of 111 (39.6%) cases of untreated CRC but was not detected in the adenoma cases. The difference in the sensitivity of mSEPT9 among patients with adenomas and those with each stage of untreated CRC was statistically significant (Dukes' staging, p = 0.002 and TNM staging, p = 0.008). The sensitivity of mSEPT9 for each of the stages (I - IV) of untreated CRC patients were 20.7%, 54.1%, 36.6%, and 75.0%, respectively. The positive mSEPT9 results in untreated CRC patients reverted to negative in 19 of 21 patients (90.5%) after treatment. CONCLUSIONS: Compared to previous studies, the overall sensitivity of mSEPT9 was lower, but similar patterns were found in the sensitivities for each stage. Additionally, mSEPT9 appeared to have potential as a monitoring tool for CRC.

Piperlongumine downregulates the expression of HER family in breast cancer cells.

HER family receptors are frequently deregulated in breast cancer and the deregulation of these receptors is associated with poor prognosis. Thus, these receptors are considered therapeutic targets. In the present study, we found that piperlongumine (PL) downregulates the expression of HER family receptors HER1, HER2, and HER3 in breast cancer cells. Downregulation of these receptors by PL is mediated through the generation of reactive oxygen species (ROS), as N-acetyl-cysteine blocks it. Interestingly, the HER2-overexpressing cell lines BT474 and SkBr3 are somewhat more sensitive to PL than the low HER2-expressing cell line MCF7. In addition, the overexpression of HER2 increases the sensitivity of MCF7 cells to PL. Collectively, our data indicate the therapeutic potential of PL in the treatment of breast cancer.

Combined effects of EGFR tyrosine kinase inhibitors and vATPase inhibitors in NSCLC cells.

Despite excellent initial clinical responses of non-small cell lung cancer (NSCLC) patients to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), many patients eventually develop resistance. According to a recent report, vacuolar H+ ATPase (vATPase) is overexpressed and is associated with chemotherapy drug resistance in NSCLC. We investigated the combined effects of EGFR TKIs and vATPase inhibitors and their underlying mechanisms in the regulation of NSCLC cell death. We found that combined treatment with EGFR TKIs (erlotinib, gefitinib, or lapatinib) and vATPase inhibitors (bafilomycin A1 or concanamycin A) enhanced synergistic cell death compared to treatments with each drug alone. Treatment with bafilomycin A1 or concanamycin A led to the induction of Bnip3 expression in an Hif-1α dependent manner. Knock-down of Hif-1α or Bnip3 by siRNA further enhanced cell death induced by bafilomycin A1, suggesting that Hif-1α/Bnip3 induction promoted resistance to cell death induced by the vATPase inhibitors. EGFR TKIs suppressed Hif-1α and Bnip3 expression induced by the vATPase inhibitors, suggesting that they enhanced the sensitivity of the cells to these inhibitors by decreasing Hif-1α/Bnip3 expression. Taken together, we conclude that EGFR TKIs enhance the sensitivity of NSCLC cells to vATPase inhibitors by decreasing Hif-1α/Bnip3 expression. We suggest that combined treatment with EGFR TKIs and vATPase inhibitors is potentially effective for the treatment of NSCLC.

Blockage of Stat3 enhances the sensitivity of NSCLC cells to PI3K/mTOR inhibition.

The PI3K/Akt/mTOR axis in lung cancer is frequently activated and implicated in tumorigenesis. Specific targeting of this pathway is therefore an attractive therapeutic approach for lung cancer. However, non-small cell lung cancer cells are resistant to BEZ235, a dual inhibitor of PI3K and mTOR. Interestingly, blockage of Stat3 with a selective inhibitor, S3I-201, or siRNA dramatically sensitized the BEZ235-induced cell death, as evident from increased PARP cleavage. Furthermore, inhibition of Stat3 led to enhancement of cell death induced by LY294002, a PI3K inhibitor. Treatment of cells with a combination of BEZ235 and S3I-201 significantly induced the proapoptotic transcription factor, CHOP, and its targets, Bim and DR4. Knockdown of CHOP or Bim suppressed cell death stimulated by the combination treatment, implicating the involvement of these BEZ235/S3I-201-induced factors in pronounced cell death. Moreover, the BEZ235/S3I-201 combination enhanced TRAIL-induced cell death. Our results collectively suggest that blockage of Stat3 presents an effective strategy to overcome resistance to PI3K/Akt/mTOR inhibition.

Inhibition of vacuolar H+ ATPase enhances sensitivity to tamoxifen via up-regulation of CHOP in breast cancer cells.

Resistance of estrogen receptor-positive breast cancer cells to tamoxifen represents a major barrier to the successful treatment of breast cancer. In the present study, we found that vacuolar H+ ATPase (vATPase) inhibitors, bafilomycin A1 and concanamycin A, sensitize tamoxifen-induced cell death. siRNA targeting ATP6V0C, a 16-kDa hydrophobic proteolipid subunit of vATPase that plays a central role in H+ transport, markedly increased cell death induced by tamoxifen. Interestingly, bafilomycin A1 induced up-regulation of DR4/DR5 and CHOP. Knock-down of CHOP by siRNA suppressed the cell death induced by bafilomycin A1 and tamoxifen, suggesting that bafilomycin A1-mediated CHOP activation sensitizes to tamoxifen. In addition, we found that bafilomycin A1 enhances TRAIL-induced cell death in breast cancer cells. Furthermore, we showed that combination of vATPase inhibitors with tamoxifen also effectively induced cell death in HER2- and ERα-overexpressing breast cancer cells. Overall, our results demonstrate that inhibition of vATPase can potentiate the apoptotic effects of tamoxifen through up-regulation of CHOP.

Cryptic KMT2A/MLLT10 fusion detected by next-generation sequencing in a case of pediatric acute megakaryoblastic leukemia.

KMT2A (11q23.3) gene rearrangements are found in acute leukemia and are associated with a poor or intermediate prognosis. MLLT10 is the fourth most common gene fusion partner for KMT2A. A reciprocal translocation t(10;11) is insufficient to produce an in-frame KMT2A/MLLT10 fusion, because the genes involved in the rearrangement have opposite transcriptional orientations. In order to bring KMT2A and MLLT10 into juxtaposition, complex rearrangements are required. Until now, conventional chromosome, fluorescence in situ hybridization (FISH), and reverse transcriptase-polymerase chain reaction (RT-PCR) studies have been used to detect KMT2A/MLLT10 fusions. However, conventional studies have limitations, such as poor and inconsistent resolution, when compared to next-generation sequencing (NGS). In this study, we report a pediatric patient with acute megakaryoblastic leukemia, in whom the cryptic KMT2A/MLLT10 fusion was not detected by KMT2A break-apart probe FISH and chromosome analysis, but detected by NGS. In this patient, NGS showed cryptic insertion of MLLT10 exons 9-24 into intron 9 of KMT2A, resulting in a KMT2A/MLLT10 fusion. Therefore, NGS is a valuable complementary option for the evaluation of structural aberrations, especially those with a cryptic size.

Distinct mutational pattern of T-cell large granular lymphocyte leukemia combined with pure red cell aplasia: low mutational burden of STAT3.

T-cell large granular lymphocyte leukemia (T-LGL) is often accompanied by pure red cell aplasia (PRCA). A high depth of next generation sequencing (NGS) was used for detection of the mutational profiles in T-LGL alone (n = 25) and T-LGL combined with PRCA (n = 16). Beside STAT3 mutation (41.5%), the frequently mutated genes included KMT2D (17.1%), TERT (12.2%), SUZ12 (9.8%), BCOR (7.3%), DNMT3A (7.3%), and RUNX1 (7.3%). Mutations of the TERT promoter showed a good response to treatment. 3 of 41 (7.3%) T-LGL patients with diverse gene mutations were revealed as T-LGL combined with myelodysplastic syndrome (MDS) after review of bone marrow slide. T-LGL combined with PRCA showed unique features (low VAF level of STAT3 mutation, low lymphocyte count, old age). Low ANC was detected in a STAT3 mutant with a low level of VAF, suggesting that even the low mutational burden of STAT3 is sufficient for reduction of ANC. In retrospective analysis of 591 patients without T-LGL, one MDS patient with STAT3 mutation was revealed to have subclinical T-LGL. T-LGL combined with PRCA may be classified as unique subtype of T-LGL. High depth NGS can enable sensitive detection of concomitant MDS in T-LGL. Mutation of the TERT promoter may indicate good response to treatment of T-LGL, thus, its addition to an NGS panel may be recommended.

Immunohistochemical Staining to Identify Concomitant Systemic Mastocytosis in Acute Myeloid Leukemia with RUNX1::RUNX1T1.

Systemic mastocytosis with associated hematological neoplasm (SM-AHN) poses diagnostic challenges because of the coexistence of atypical mast cell proliferation and hematological neoplasms. We assessed the presence of SM-AHN in patients with acute myeloid leukemia (AML) with RUNX1::RUNX1T1 from 2014 to 2020. Bone marrow (BM) samples were evaluated for mast cell aggregates using CD117 and CD25 immunohistochemical (IHC) staining. The KIT D816V variant burden at diagnosis and post induction was assessed using droplet digital PCR. Among 23 patients diagnosed as having AML with RUNX1::RUNX1T1, four (17.4%) were also diagnosed as having SM-AHN. No significant differences in clinical characteristics or overall survival (P=0.565) were observed between patients with or without SM-AHN, except for the presence of KIT variants (P=0.040). After induction therapy, IHC staining revealed the presence of mast cell aggregates in the BM, and the KIT D816V variant burden decreased with decreasing blast count and was similar in BM aspirates, smear slides, and sections. Concomitant SM-AHN was not infrequent in AML patients with RUNX1::RUNX1T1. This study showed the importance of CD117 and CD25 IHC staining after induction chemotherapy for SM-AHN screening, especially in patients with KIT variants.

Myelodysplastic syndromes and overlap syndromes.

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematological neoplasms characterized by ineffective hematopoiesis, morphologic dysplasia, and cytopenia. MDS overlap syndromes include various disorders, such as myelodysplastic/myeloproliferative neoplasms and hypoplastic MDS with aplastic anemia characteristics. MDS overlap syndromes share the characteristics of other diseases, which make differential diagnoses challenging. Advances in genomic studies have led to the discovery of frequent mutations in MDS and overlap syndromes; however, most of the mutations are not specific for the diagnosis of these diseases. The molecular characteristics of the overlap syndromes usually do not show a just "in-between" form but rather heterogeneous features. Established diagnostic criteria for these diseases based on clinical, morphologic, and laboratory features are still useful when combined with genomic data. It is expected that further studies for MDS and overlap syndromes will place emphasis on the roles of mutations as therapeutic targets and prognostic indicators.

Recurrent parvovirus B19 infection-associated pure red cell aplasia in a kidney transplant patient.

Posttransplant anemia is a common complication after kidney transplantation. Parvovirus B19 (PVB19) infection can induce pure red cell aplasia (PRCA) in immunosuppressed transplant patients. We herein report a case of recurrent PVB19-associated PRCA in a kidney transplant patient. A 49-year-old woman presented with anemia and normal renal function 1 year after a deceased-donor kidney transplantation for immunoglobulin A nephropathy-related end-stage renal disease. She received desensitization therapy, and 2 years later, she underwent transplantation with thymoglobulin induction. Despite repeated red cell transfusion and erythropoietin therapy, her anemia aggravated progressively. Bone marrow biopsy revealed normocytic normochromic PRCA. Real-time polymerase chain reaction detected a high plasma load of PVB19. Administration of intravenous immunoglobulin (IVIG) at 2 g/kg with adjuvant reduction of tacrolimus and discontinuation of myfortic acid effectively treated the anemia. However, the PVB19 load remained high, and PRCA recurred 7 months after the initial IVIG treatment. Tacrolimus was switched to cyclosporine in the second IVIG treatment, which successfully improved PRCA and reduced the PVB19 load. Our case suggested that PVB19-associated PRCA should be suspected when persistent anemia is observed in kidney transplant patients with heavy immunosuppression and that PVB19-associated PRCA can recur in the presence of persistent PVB19 viremia.

Application of Fluorescence In Situ Hybridization on Cerebrospinal Fluid Cytospins for the Detection of Residual Leukemic Cells in Patients With Childhood Acute Lymphoblastic Leukemia.

OBJECTIVES: Diagnosis of central nervous system involvement in acute lymphoblastic leukemia (ALL) requires morphologic expertise; therefore, we evaluated interphase fluorescence in situ hybridization (iFISH) of cerebrospinal fluid (CSF) cytospin preparations as a potential complementary test. METHODS: Twenty-three CSF cytospin specimens from 13 pediatric patients with ALL were included. iFISH probes detecting BCR-ABL1, ETV6-RUNX1, and KMT2A rearrangement and CDKN2A deletion, which were present at initial diagnosis, were used on follow-up CSF cytospin specimens and were compared with cytology. RESULTS: Seventeen (73.9%) follow-up specimens showed concordant results between iFISH and cytology. Two (8.7%) samples with discordant results were positive by iFISH but not by cytology; one (4.3%) was positive only by cytology. In the remaining three (13.0%) specimens, too few cells were available for cytology, whereas iFISH interpretation was possible. CONCLUSIONS: iFISH of CSF cytospin preparations improves malignant cell detection in pediatric ALL.

Monozygotic twins with shared de novo GATA2 mutation but dissimilar phenotypes due to differential promoter methylation.

A revised WHO classification of hematopoietic neoplasm introduced the new category 'Myeloid Neoplasms with Germline Predisposition', reflecting the growing importance of genetic testing for myeloid neoplasms. Here, we investigated monozygotic twins with the same de novo mutation in GATA2 but different phenotypes. The patient suffering a bleeding tendency was diagnosed with myelodysplastic syndrome (MDS), and her monozygotic twin showed dysmegakaryopoietic features in the bone marrow. Targeted sequencing revealed the same germline mutation in GATA2, c.1192C > T, in both sisters and different somatic mutations in 14 genes between the sisters. The GATA2 mutation was absent in both parents, and their hemograms were normal. The methylation profile of the GATA2 promoter region was different between the twins, showing denser promoter methylation in the patient, correlated with MDS. Thus, we concluded that the twins had acquired a de novo GATA2 mutation but showed different phenotypes, possibly due to the critical role of epigenetic changes.

Induction of HSP27 and HSP70 by constitutive overexpression of Redd1 confers resistance of lung cancer cells to ionizing radiation.

Redd1 is a stress response protein that functions as a repressor of mTORC1, a central regulator of protein translation, resulting in the inhibition of cell growth and metabolism. However, paradoxically, high Redd1 expression favors cancer progression and generates resistance to cancer therapy. Herein, we revealed that constitutive overexpression of Redd1 induced HSP27 and HSP70 expression in lung cancer cells. The expression of Redd1, HSP27 and HSP70 was highly increased in lung cancer tissues compared with that in normal lung tissues. Inhibition of HSP27 or HSP70 suppressed AKT phosphorylation, which was induced by constitutive overexpression of Redd1 and enhanced the inhibitory effects on viability of Redd1­overexpressing cells. Inhibition of AKT phosphorylation resulted in a decrease of HSP27 and HSP70 expression in Redd1­overexpressing cells. These data indicated that HSPs and AKT in Redd1­overexpressing cells positively regulated the function and expression of each other and were involved in lung cancer cell survival. Knockdown of HSP27, HSP70 or AKT enhanced ionizing radiation (IR) sensitivity, particularly in lung cancer cells in which Redd1 was stably overexpressed. Collectively, constitutive overexpression of Redd1 led to HSP27 and HSP70 induction and AKT activation, which were involved in lung cancer cell survival and resistance to IR, suggesting that Redd1 may be used as a therapeutic target for lung cancer.

Replicative senescence of hematopoietic cells in patients with idiopathic cytopenia of undetermined significance.

We hypothesized that a subset of idiopathic cytopenia of undetermined significance (ICUS) is associated with an increased autonomous proliferation with exhaustion of hematopoiesis. The aim of this study was to investigate the cell turnover rate and replicative history of the bone marrow cells of ICUS patients. To this end, we examined telomere length (TL), proliferation, and apoptosis of the bone marrow cells of ICUS patients and healthy controls (HCs) using telomere quantitative fluorescence in situ hybridization and immunohistochemical staining for Ki-67 and cleaved caspase-3. We also performed targeted sequencing of 88 myeloid-associated genes. A total of 37 patients with ICUS were enrolled in this study, with a median age of 66 years (range: 31-83). TLs were significantly shorter in patients with ICUS than in the HCs (8.8, interquartile range [IQR] 6.8-12.1 vs 18.4, IQR 14.4-22.0, p < 0.0001). Proliferation (Ki-67-positive) and apoptosis (cleaved caspase-3-positive) were significantly increased in patients with ICUS compared to HCs (median = 20.0% vs 5.0%, p = 0.0003; 45.0% vs 22.5%, p = 0.0005, respectively). The shortening of TL and the increased proliferation and apoptotic activity was also prominent in patients with ICUS without mutation and dysplasia than in HCs (p < 0.0001, p < 0.0001, and p = 0.0093, respectively). TL was not associated with mutational profile and clinical characteristics as well in patients with ICUS. To our knowledge, this is the first study to show that ICUS is associated with premature replicative senescence with increased proliferation and apoptosis of bone marrow cells. Further study is needed to address the cause of replicative exhaustion in ICUS patients.

Utilization of Archived Plasma to Detect Epidermal Growth Factor Receptor Mutation in Non-Small Cell Lung Cancer Patients.

Precision medicine has received increased attention as an effective approach for the treatment of cancer patients. Because of challenges associated with the availability of archived tissue, liquid biopsies are often performed to detect cancer-specific mutations. One of the major advantages of the liquid biopsy is that the treatment can be monitored longitudinally, even after the tumor tissue is no longer available. In a clinical setting, one component of precision medicine is the detection of cancer-specific mutations using archived samples. In this study, we evaluated the epidermal growth factor receptor (EGFR) mutation status of samples of lung cancer patients stored before introduction of the plasma EGFR test at our institution. The aim of this study was to validate the utility of archived plasma samples for detection of the EGFR mutation in nonsmall cell lung cancer (NSCLC) patients. The Cobas® EGFR Mutation Test v2 was the first liquid biopsy test approved as a companion diagnostic test for patients with NSCLC treated with tyrosine kinase inhibitors. We tested for the EGFR mutation in 116 plasma samples archived in the biobank, and the results were compared with those obtained in the tissue or cytology EGFR mutation test. The EGFR mutation-positive rate from archived plasma was lower than that determined from tissue or cytology at 19.0% and 53.4%, respectively, and the concordance rate between the two tests was 58.6%. Of interest, five (4.3%) samples showed the T790M mutation in the plasma test, whereas this mutation was only detected in two (1.7%) tissue/cytology samples. Five (4.3%) samples were additionally positive in the plasma test. Overall, these results indicate that archived plasma samples can serve as an alternative source for the plasma EGFR mutation test when tissue samples are not available, and can improve precision medicine and long-term follow-up in a noninvasive manner.