A case of pancreatic neuroendocrine tumor in a patient with neurofibromatosis-1

ABSTRACT: Patients with neurofibromatosis-1 (NF-1) sometime develops neuroendocrine tumors (NET). Although these NETs usually occur in the duodenum or peri-ampullary region, they occasionally grow in the pancreas (PNET). A 62-year-old man with NF-1 had mild liver dysfunction and was admitted to our hospital for further examination. An abdominal contrast enhanced computed tomography scan demonstrated a 30 mm tumor in the head of the pancreas. The scan showed showed an invasion of the tumor into the duodenum, and biopsy under an endoscopic ultrasonography indicated that the tumor was a NET. A subtotal stomach-preserving pancreaticoduodenectomy was performed. Macroscopically, the pancreatic tumor was white and elastic hard. Microscopically, tumor cells were composed of ribbons, cords, and solid nests with acinus-like structure. The tumor was diagnosed as NET G2 according to WHO classification (2010). The product of NF-1 gene, i.e., neurofibromin, was weakly positive in the tumor cells, suggesting that the tumor was induced by a mutation in the NF-1 gene. This is the seventh case of PNET arising in NF-1 patients worldwide.     

Early duodenal adenocarcinoma resembling a submucosal tumor cured with endoscopic resection: a case report

ABSTRACT: INTRODUCTION: Primary adenocarcinomas resembling submucosal tumors are rare in the gastrointestinal tract. Almost all the submucosal tumor-like adenocarcinomas previously reported invaded the submucosa or deeper. Therefore, submucosal tumor-like lesions are usually treated by surgical resection, and those that arise in the duodenum have been treated by pancreaticoduodenectomy. CASE PRESENTATION: A 65-year-old Japanese man was diagnosed with a submucosal tumor-like adenocarcinoma in his duodenum. We considered it possible that the tumor invasion was limited to the mucosal or submucosal layers and could be removed by endoscopic resection. Tumor histopathology revealed a well-differentiated adenocarcinoma confined to the muscularis mucosae with no lymphovascular invasion. Complete resection of the carcinoma was achieved and there has been no recurrence three years after endoscopic resection. CONCLUSIONS: We suggest that submucosal tumor-like adenocarcinomas arising in nonampullary duodenal sites should be diagnosed carefully with a view to possible endoscopic resection.     

Endoscopic ultrasound-guided fine needle aspiration cytology of pancreatic neuroendocrine tumours: cytomorphological and immunocytochemical evaluation

OBJECTIVES: Endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) is increasingly used in preoperative localization and diagnosis of pancreatic neoplasms including neuroendocrine tumours (NETs). The objective of the present study was to identify the cytological features of pancreatic NETs obtained by EUS-FNA. METHODS: The study group consisted of nine cases of pancreatic tumours correctly diagnosed or strongly suggestive of NETs based on EUS-FNA. Cytological smears were retrospectively reviewed. The clinical data and immunocytochemical stains applied to the cell block preparations were also reviewed and examined. RESULTS: All cases except one showed characteristic cytomorphological features sufficient for their recognition and separation from pancreatic adenocarcinoma and other lesions. The most helpful cytological features that facilitated the cytological diagnosis of NET were a richly cellular aspirate with a monotonous, poorly cohesive population of small cells with a speckled or dusty chromatin pattern and plasmacytoid morphology. The neuroendocrine differentiation of these tumours was further confirmed by immunocytochemistry. CONCLUSION: EUS-FNA is a valuable method in the recognition of pancreatic NETs. By adherence to the characteristic cytomorphological criteria of pancreatic NET together with collection of suitable material for ancillary immunocytochemical stains, cytopathologists could reach a correct diagnosis in most instances.     

Cytologic features of premalignant glandular lesions in the upper gastrointestinal tract

The cytologic findings in 13 endoscopic brushing specimens from biopsy-proven premalignant glandular lesions (PGLs) of the upper gastrointestinal tract were reviewed retrospectively. The specimens were from ten patients: three with dysplasia in Barrett's esophagus, four with gastric adenomas and three with duodenal adenomas. One dysplasia in Barrett's esophagus and four adenomas (two gastric and two duodenal) had coexisting adenocarcinomas. Most pure PGLs were characterized cytologically by cohesive three-dimensional clusters of cells with more-or-less uniformly enlarged nuclei and an increased nuclear/cytoplasmic ratio. Crowding and molding were present within these clusters; however, the cells were arranged in a somewhat orderly or palisading fashion, instead of entirely haphazardly. In cases of carcinoma coexisting with adenoma or dysplasia, the atypical cells tended to be more pleomorphic and dyshesive. In one specimen from an adenocarcinoma arising in an adenoma, the adenomatous and carcinomatous components could be distinguished cytologically.     

Cushing Syndrome Secondary to A Thymic Carcinoid Tumor Due to Multiple Endocrine Neoplasia Type 1

ObjectiveTo present an Iranian patient with a nonclassic form of multiple endocrine neoplasia type 1 (MEN 1) who presented with ectopic Cushing syndrome (CS) secondary to a corticotropin (ACTH)-producing thymic neuroendocrine tumor (NET), recurrent renal stones, and a giant cell granuloma of the jaw due to primary hyperparathyroidism (PHPT) without involvement of the pituitary or pancreas.MethodsRelevant imaging and hormonal evaluations were performed. The patient was operated on 2 occasions for a thymic NET and on 3 occasions for PHPT. DNA from a peripheral blood sample was extracted for sequencing of the MEN1 gene.ResultHistopathologic evaluation of the thymic tumor removed during the first surgery showed an atypical carcinoid tumor with a Ki-67 labeling index of 5%. Evaluation after the second surgery revealed an invasive carcinoid tumor with a Ki-67 labeling index of 30%.Parathyroid pathology was suggestive of glandular hyperplasia. Menin gene sequencing revealed a novel frameshift mutation c.1642_1648dup in exon 10.ConclusionThis case of MEN 1 is unusual because most thymic NETs in MEN 1 are nonfunctional, and secretion of ACTH or other ectopic hormones rarely occurs. In patients presenting with thymic NETs, the possibility of MEN 1 should be considered, especially in the presence of hyperparathyroidism. This case also demonstrates that the behavior of thymic NETs can change over time from slow-growing tumors to highly invasive neoplasia, and that ectopic ACTH can be produced by these tumors in the context of MEN 1. (Endocr Pract. 2011;17:e92-e96)     

Fine needle aspiration cytology and core biopsy histology in infiltrating syringomatous adenoma of the breast. A case report

BACKGROUND: Infiltrating syringomatous adenoma is a rare tumor of the breast that can radiologically mimic invasive duct carcinoma. Detailed fine needle aspiration cytology and needle core biopsy findings on this lesion have not been previously described. CASE: The clinical, radiologic and pathologic findings of an infiltrating syringomatous adenoma of the breast in a 71-year-old female who presented with a subareolar lump are described. The cytology of the tumor was characterized by a combination of a background of plump, fibroblastoid cells and cohesive sheets of bland epithelial cells. Histologically the tumor showed infiltrating, duct-like structures with squamous metaplasia and a desmoplastic stroma. CONCLUSION: Fine needle aspiration cytology and needle core biopsy can distinguish infiltrating syringomatous adenoma from malignant disease of the breast.     

Immunohistochemical estimation of in-situ cell cycle time in neoplastic epithelial cells in human large intestine: a new cell proliferation index

In-situ cell cycle time (in-situ Tc) of epithelial cells could be estimated by using a formula; in-situ Tc = cell proliferation rate divided by mitosis rate, on a scale of Tm (cell cycle time in M phase) arbitrary unit (AU), In order to see the nature of in-situ Tc in the adenoma-carcinoma sequence in the human large intestine, the in-situ Tc in 27 cases of adenoma and 71 cases of adenocarcinoma with adenoma components in the human large intestine was estimated by using this formula, counting proliferating cells and mitotic cells in the immunohistochemistry of Ki-67 antigen. C12 antigen was examined as an oncogenic progression indicator in the adenoma-carcinoma sequence. The in-situ Tc tended to shorten in adenoma in accordance with the histological grading of atypia but not in adenoma component. No significant differences in the in-situ Tc was recognized as a whole among adenomas, adenoma components and adenocarcinomas in the mucosa, whereas the in-situ Tc of adenoma components with moderate to severe atypia was significantly longer than that of adenocarcinomas in the mucosa (p = 0.05). The in-situ Tc lengthened in adenocarcinomas invading the submucosa and shortened in adenocarcinomas invading the proper muscular layer. The cases expressing the C12 antigen increased in order of adenoma, adenoma component and adenocarcinoma. The cases expressing the C12 antigen indicated short in situ Tc in the adenomas and adenocarcinomas but not in the adenoma components. Thus, the estimated in-situ Tc is a useful index of the oncogenetic progression, which is different from that detected by the C12 antigen.     

原发性胃淋巴瘤临床与内镜特征分析

目的:探讨影像学检查及胃镜、超声内镜对原发性胃淋巴瘤的术前诊断方法,以提高该疾病的术前诊断率。方法:总结我院经手术及病理证实的21例原发性胃淋巴瘤资料,评估胃镜活检、超声内镜及CT对该病诊断的作用。结果:21例术前CT检查,误诊为浸润型胃癌11例,间质瘤2例,未见明显异常3例。CT术前诊断率为23.8%(5/21)。全部患者均实施胃镜检查,活检病理诊断淋巴瘤14例,胃镜活检诊断率为66.7%(14/21)。其中10名患者实施超声胃镜检查,判断胃淋巴瘤6例、胃癌3例、间质瘤1例;术前诊断率为60.0%(6/10)。结论:胃镜及超声内镜是原发性胃淋巴瘤的主要术前诊断方式;CT扫描能明确有无纵隔及腹腔内淋巴结肿大,为原发性胃淋巴瘤提供诊断依据。     

Whole body diffusion for metastatic disease assessment in neuroendocrine carcinomas: comparison with OctreoScan(R) in two cases

ABSTRACT: Neuroendocrine tumor (NET) patients must be adequately staged in order to improve a multidisciplinary approach and optimal management for metastatic disease. Currently available imaging studies include somatostatin receptor scintigraphy, like OctreoScan(R), computed tomography (CT), scans and magnetic resonance imaging (MRI), which analyze vascular concentration and intravenous contrast enhancement for anatomic tumor localization. However, these techniques require high degree of expertise for interpretation and are limited by their availability, cost, reproducibility, and follow-up imaging comparisons. NETs significantly reduce water diffusion as compared to normal tissue. Diffusion-weighted imaging (DWI) in MRI has an advantageous contrast difference: the tumor is represented with high signal over a black normal surrounding background. The whole-body diffusion (WBD) technique has been suggested to be a useful test for detecting metastasis from various anatomic sites. In this article we report the use of DWI in MRI and WBD in two cases of metastatic pulmonary NET staging in comparison with OctreoScan(R) in order to illustrate the potential advantage of DWI and WBD in staging NETs.     

The clinicopathological significance of angiogenesis in hindgut neuroendocrine tumors obtained via an endoscopic procedure

Background

As the World Health Organization grading system for gastroenteropancreatic-neuroendocrine tumors (GEP-NETs) may not always correlate with tumor progression, it is imperative that other independent predictors of tumor progression be established. To identify such predictors, we conducted a retrospective histopathological study of hindgut NETs, obtained from endoscopic procedures, and used statistical analyses to evaluate predictive factors.

Methods

We first obtained clinicopathological data of cases of hindgut NETs. Tissue sections from tumor samples were prepared and subjected to pathological examination. In particular, we calculated the microvessel density (MVD) and lymphatic microvessel density (LMVD) values, and performed appropriate statistical analyses.

Results

A total of 42 cases of hindgut NETs were selected for the study, 41 from the rectum and 1 from the sigmoid colon. Based on the Ki-67 labeling index, 34 cases were classified as NET G1 tumors and 8 as NET G2 tumors. MVD values ranged from 1.4/mm² to 73.9/mm² and LMVD values from 0/mm² to 22.9/mm². MVD and LMVD were identified as risk factors for venous and lymphatic invasion of hindgut NETs. Moreover, MVD positively correlated with the maximum diameter of the tumor.

Conclusions

Tumor progression of NETs may cause angiogenesis and lymphangiogenesis, via an unknown mechanism, as well as lymphovascular invasion. Angiogenesis likely plays an important role in occurrence and progression in the initial phase of hindgut NETs.

     

Cytokine-producing function of human blood cells in chronic atrophic gastritis and gastric adenomas and adenocarcinomas

The cytokine-producing potential of blood cells has been studied in the atrophic gastritis–adenoma–adenocarcinoma progression of pathological states of the stomach. It has been revealed that, at the initial stage of carcinogenesis, namely adenoma, immunocompetent cells have the highest cytokine-producing proto-oncogenic potential as compared to both atrophic gastritis, which presents a precancerous condition, and completely formed malignant tumor (gastric adenocarcinoma).     

Composite neuroendocrine tumor and adenocarcinoma of the rectum

Background

Although adenocarcinomas showing neuroendocrine differentiation or those mixed with high-grade neuroendocrine carcinoma (NEC) are sometimes encountered, composite tumors comprising neuroendocrine tumor (NET) Grade 1 and adenocarcinoma are exceedingly rare.

Case presentation

A 64-year-old male presented after testing positive for fecal occult blood at a medical check-up. A biopsy demonstrated the presence of a NET and endoscopic submucosal dissection was undertaken. Histologic examination revealed that a well differentiated tubular adenocarcinoma was present in addition to the NET. Furthermore, histological transition between the two tumors was evident. Accordingly, this case was considered to be a composite tumor comprising NET and adenocarcinoma.

Conclusion

Composite tumors consisting of NET Grade 1 and adenocarcinoma are exceedingly rare, and only a few examples have been reported hitherto.

     

Two cytologic patterns in invasive ductal adenocarcinoma of the pancreas

OBJECTIVE: To clarify 2 cytologic patterns: severe ductal dysplasia (SD)/carcinoma in situ (CIS) and invasive components of invasive ductal adenocarcinoma of the pancreas (IDAP). STUDY DESIGN: Tumor samples from 12 patients with IDAP were examined cytologically and histologically. Cytologic specimens were obtained by fine needle aspiration (ENA) and imprint smears from resected pancreases. RESULTS: In the 12 IDAP cases, roughly 2 cell populations, SD/CIS-type cells and invasive component-type cells, were detected cytologically. The former composed a small portion of the tumor cells, exhibited a small nuclei without anisonucleosis and had a decreased total quantity of chromatin as compared with invasive component-type cells. SD/CIS-type cells were found in small papillary-cohesive and compactly packed clusters and had clearly defined cytoplasmic borders, a nucleus individually enveloped in well-preserved cytoplasm and small amount of cytoplasm (< 15 microm in short diameter) without prominent anisocytosis. The latter comprised mostly of the tumor cells, were present characteristically as a loose and discohesive population and contained a combination of hyperchromatin, large nuclei (> 15 microm) and abundant cytoplasm (>21 microm). Histologically, these 12 cases exhibited IDAP with SD/CIS. Hence, the invasive component-type cells appeared to originate with ordinary invasive spread of IDAP, and the SD/CIS type cells appeared to originate with noninvasive intraductal spread. CONCLUSION: Two cytologic patterns originating with SD/CIS and invasive components of IDAP could be differentiated.     

Second Cancers in Patients with Neuroendocrine Tumors

Background

Second cancers have been reported to occur in 10-20% of patients with neuroendocrine tumors (NETs). However, most published studies used data from a single institution or focused only on specific sites of NETs. In addition, most of these studies included second cancers diagnosed concurrently with NETs, making it difficult to assess the temporality and determine the exact incidence of second cancers. In this nationwide population-based study, we used data recorded by the Taiwan Cancer Registry (TCR) to analyze the incidence and distribution of second cancers after the diagnosis of NETs.

Methods

NET cases diagnosed from January 1, 1996 to December 31, 2006 were identified from the TCR. The data on the occurrence of second cancers were ascertained up to December 31, 2008. Standardized incidence ratios (SIRs) of second cancers were calculated based on the cancer incidence rates of the general population. Cox-proportional hazards regression analysis was performed to estimate the hazard ratio (HR) and 95% confidence interval (CI) for the risk of second cancers associated with sex, age, and primary NET sites.

Results

A total of 1,350 newly diagnosed NET cases were identified according to the selection criteria. Among the 1,350 NET patients, 49 (3.63%) developed a second cancer >3 months after the diagnosis of NET. The risk of second cancer following NETs was increased compared to the general population (SIR = 1.48, 95% CI: 1.09-1.96), especially among those diagnosed at age 70 or older (HR = 5.08, 95% CI = 1.69-15.22). There appeared to be no preference of second cancer type according to the primary sites of NETs.

Conclusions

Our study showed that the risk of second cancer following NETs is increased, especially among those diagnosed at age 70 or older. Close monitoring for the occurrence of second cancers after the diagnosis of NETs is warranted.     

Can abundant colloid exclude oncocytic (Hürthle cell) carcinoma in thyroid fine needle aspiration? Cytohistological correlation of 127 oncocytic (Hürthle cell) lesions

Objective:  The objective of the present study was to find out whether the presence or absence of certain cytological features can exclude oncocytic (Hürthle cell) carcinoma in thyroid fine needle aspiration (FNA) to minimize unnecessary surgery. Methods:  Over a 17‐year period, 127 hypercellular, oncocyte‐exclusive, lymphocyte‐absent aspirates obtained via ultrasound‐guided FNA with on‐site assessment had histology slides for review. The presence or absence of six cytological features (microfollicular arrangement, discohesive single cells, small cell dysplasia, large cell dysplasia, transgressing blood vessels and colloid) and one histological feature (macrofollicular component) were determined for each case independently by two cytopathologists. Results:  Histology showed 12 (9.4%) cases of Hashimoto thyroiditis, 23 (18.1%) oncocytic adenomatoid nodules in nodular goitre, 66 (52.0%) oncocytic adenomas and 26 (20.5%) oncocytic carcinomas (13 minimally invasive without angioinvasion, six minimally invasive with angioinvasion, seven widely invasive). Histologically, a macrofollicular component was present in seven of 26 (26.9%) oncocytic carcinomas, including one case with abundant thin colloid. A microfollicular arrangement, discohesive single cells, small cell dysplasia, large cell dysplasia and transgressing vessels were present in oncocytic carcinoma, oncocytic adenoma and oncocytic adenomatoid nodules in nodular goitre. Conclusions:  A macrofollicular component is frequently present in oncocytic carcinoma, oncocytic adenoma and oncocytic adenomatoid nodules in nodular goitre. None of the cytological features studied, including abundant colloid, can exclude oncocytic carcinoma. Oncocytic carcinoma can only be excluded by thorough histological examination of thyroidectomy specimens. A molecular marker is needed to triage oncocytic lesions in thyroid FNA.     

Multiple cystic sweat gland tumors in transgenic mice

Here we describe gross and microscopic sweat gland tumors found in a transgenic mouse model of breast cancer, which had transforming growth factor α under the control of mouse mammary tumor virus promoter (MMTV-TGFα). Initially, 20% of the mice in the colony were affected. Cystic lesions formed on the phalanges, palmar surfaces of the metacarpals, and plantar surfaces of the metatarsals. The lesions were multifocal and nonulcerated with straw-colored fluid, ranging in size from 1 to 30 mm at the largest dimension. The colony was monitored for 6 mo; during that time, the prevalence of lesions increased to 52% of the mice. Histologically, in most cases the cyst walls were lined by 1 or 2 layers of normal-appearing epithelial cells that resembled basal cells, indicating adenoma. However, 2 cysts from 2 different mice had papillary proliferative projections and extensive disorganized glandular structures that protruded into the cyst cavities, indicating adenocarcinoma. In these 2 cases, the neoplastic cells revealed architectural and cytologic atypia with rare mitoses. Similar findings have previously been observed in sweat gland tumors; however, multiple sweat-gland tumors have not been reported in mice.     

In vitro resistance mechanisms of Neisseria meningitidis against neutrophil extracellular traps

Neisseria meningitidis (Nm) is a leading cause of septicemia in childhood. Nm septicemia is unique with respect to very quick disease progression, high in vivo bacterial replication rate and its considerable mortality. Nm circumvents major mechanisms of innate immunity such as complement system and phagocytosis. Neutrophil extracellular traps (NETs) are formed from neutrophils during systemic infection and are suggested to contain invading microorganisms. Here, we investigated the interaction of Nm with NETs. Both, meningococci and spontaneously released outer membrane vesicles (SOMVs) were potent NET inducers. NETs were unable to kill NET bound meningococci, but slowed down their proliferation rate. Using Nm as model organism we identified three novel mechanisms how bacteria can evade NET‐mediated killing: (i) modification of lipid A of meningococcal LPS with phosphoethanolamine protected Nm from NET‐bound cathepsin G; (ii) expression of the high‐affinity zinc uptake receptor ZnuD allowed Nm to escape NET‐mediated nutritional immunity; (iii) binding of SOMVs to NETs saved Nm from NET binding and the consequent bacteriostatic effect. Escape from NETs may contribute to the most rapid progression of meningococcal disease. The induction of NET formation by Nm in vivo might aggravate thrombosis in vessels ultimately directing to disseminated intravascular coagulation (DIC).     

Apoptosis regulating genes in neuroendocrine tumors

Neuroendocrine tumors (NETs) are a heterogeneous group of neoplasms. They are relatively uncommon and characterised by a relatively indolent clinical course. The indolent nature of NETs has long been enigmatic and recent advances in apoptosis research have led to speculation regarding the role of programmed cell death in NET tumorigenesis. It is hoped that a fundamental molecular understanding will help explain these variant behaviors that are so evident to the clinician, and ultimately yield novel and more effective therapies. Recent studies have demonstrated that deregulation of programmed cell death may be a critical component in the multistep tumorigenesis of NETs and that the frequent expression of the BCL-2 oncoprotein in these tumors may contribute to their pathogenesis. The genetic complementation of simultaneously deregulated BCL-2 and c-MYC may be implicated in the multistep tumorigenesis of human NETs. It is also clear that numerous cellular gene products can and will be shown to impact upon apoptosis in NETs; some of these may even be molecules identified as oncoproteins or tumor suppressors. The major challenge will be to ascribe primary pathogenetic significance to tumor-associated derangements in expression of these molecules, and hopefully to then exploit our knowledge toward therapeutic benefit.     

SNCG 在胃癌中的表达及意义

目的:探讨SNCG在胃癌及正常胃粘膜组织中的蛋白和mRNA表达及其与临床病理特征的关系。方法:采用免疫组织化学SP法检测90例胃癌及40例正常胃粘膜组织中SNCG蛋白表达情况,同时应用RT-PCR检测29例胃癌及15例正常胃粘膜组织中SNCG mRNA的表达情况。结果:SNCG蛋白在胃癌组中的表达高于正常胃粘膜组(Uc=7.149,P<0.05),胃癌组中SNCG蛋白阳性表达与癌组织的浸润深度以及有无淋巴结转移有关(Uc=2.742,Uc,3.970,P均<0.05),而与患者的性别、年龄、及癌组织的分化程度无关。SNCG mRNA在胃癌组织中的表达量明显高于正常胃粘膜组织(t=4.399,P<0.01)。结论:SNCG在胃癌组织中的高表达与胃癌发生发展及浸润转移密切相关,可能会成为胃癌早期发现、早期诊断以及判断转移、预后的重要参考指标。     

Pyocyanin-Enhanced Neutrophil Extracellular Trap Formation Requires the NADPH Oxidase

Beyond intracellular killing, a novel neutrophil-based antimicrobial mechanism has been recently discovered: entrapment and killing by neutrophil extracellular traps (NETs). NETs consist of extruded nuclear DNA webs decorated with granule proteins. Although NET formation is an important innate immune mechanism, uncontrolled NET release damages host tissues and has been linked to several diseases including cystic fibrosis (CF). The major CF airway pathogen Pseudomonas aeruginosa establishes chronic infection. Pseudomonas imbedded within biofilms is protected against the immune system, but maintains chronic inflammation that worsens disease symptoms. Aberrant NET release from recruited neutrophils was found in CF, but the underlying mechanisms remain unclear. One of the most important Pseudomonas virulence factors is pyocyanin, a redox-active pigment that has been associated with diminished lung function in CF. Here we show that pyocyanin promotes NET formation in a time- and dose-dependent manner. Most CF Pseudomonas clinical isolates tested produce pyocyanin in vitro. Pyocyanin-derived reactive oxygen species are required for its NET release. Inhibitor experiments demonstrated involvement of Jun N-terminal Kinase (JNK) and phosphatidylinositol 3-Kinase (PI3K) in pyocyanin-induced NET formation. Pyocyanin-induced NETs also require the NADPH oxidase because NET release in chronic granulomatous disease neutrophils was greatly reduced. Comparison of neutrophils from gp91phox- and p47phox-deficient patients revealed that pyocyanin-triggered NET formation is proportional to their residual superoxide production. Our studies identify pyocyanin as the first secreted bacterial toxin that enhances NET formation. The involvement of NADPH oxidase in pyocyanin-induced NET formation represents a novel mechanism of pyocyanin toxicity.