Universal lung epithelium DNA methylation markers for detection of lung damage in liquid biopsies.

BACKGROUND: Circulating biomarkers for lung damage are lacking. Lung epithelium-specific DNA methylation patterns can potentially report the presence of lung-derived cell-free DNA (cfDNA) in blood, as an indication of lung cell death. METHODS: We sorted human lung alveolar and bronchial epithelial cells from surgical specimens, and obtained their methylomes using whole-genome bisulfite sequencing. We developed a PCR sequencing assay determining the methylation status of 17 loci with lung-specific methylation patterns, and used it to assess lung-derived cfDNA in the plasma of healthy volunteers and patients with lung disease. RESULTS: Loci that are uniquely unmethylated in alveolar or bronchial epithelial cells are enriched for enhancers controlling lung-specific genes. Methylation markers extracted from these methylomes revealed that normal lung cell turnover probably releases cfDNA into the air spaces, rather than to blood. People with advanced lung cancer show a massive elevation of lung cfDNA concentration in blood. Among individuals undergoing bronchoscopy, lung-derived cfDNA is observed in the plasma of those later diagnosed with lung cancer, and to a lesser extent in those diagnosed with other lung diseases. Lung cfDNA is also elevated in patients with acute exacerbation of COPD compared with patients with stable disease, and is associated with future exacerbation and mortality in these patients. CONCLUSIONS: Universal cfDNA methylation markers of normal lung epithelium allow for mutation-independent, sensitive and specific detection of lung-derived cfDNA, reporting on ongoing lung injury. Such markers can find broad utility in the study of normal and pathologic human lung dynamics.

The Role Played by Transcription Factor E3 in Modulating Cardiac Hypertrophy.

Transcription factor E3 (TFE3), which is a key regulator of cellular adaptation, is expressed in most tissues, including the heart, and is reportedly overexpressed during cardiac hypertrophy. In this study, TFE3's role in cardiac hypertrophy was investigated. To understand TFE3's physiological importance in cardiac hypertrophy, pressure-overload cardiac hypertrophy was induced through transverse aortic constriction (TAC) in both wild-type (WT) and TFE3 knockout mice (TFE3-/-). Eleven weeks after TAC induction, cardiac hypertrophy was observed in both WT and TFE3-/- mice. However, significant reductions in ejection fraction and fractional shortening were observed in WT mice compared to TFE3-/- mice. To understand the mechanism, we found that myosin heavy chain (Myh7), which increases during hemodynamic overload, was lower in TFE3-/- TAC mice than in WT TAC mice, whereas extracellular signal-regulated protein kinases (ERK) phosphorylation, which confers cardioprotection, was lower in the left ventricles of WT mice than in TFE3-/- mice. We also found high expressions of TFE3, histone, and MYH7 and low expression of pERK in the normal human heart compared to the hypertensive heart. In the H9c2 cell line, we found that ERK inhibition caused TFE3 nuclear localization. In addition, we found that MYH7 was associated with TFE3, and during TFE3 knockdown, MYH7 and histone were downregulated. Therefore, we showed that TFE3 expression was increased in the mouse model of cardiac hypertrophy and tissues from human hypertensive hearts, whereas pERK was decreased reversibly, which suggested that TFE3 is involved in cardiac hypertrophy through TFE3-histone-MYH7-pERK signaling.

Hygroscopic sonographically detectable clips form characteristic breast and lymph node pseudocysts.

The use of hygroscopic sonographically detectable clips (HSDCs) has dramatically increased during the last years, especially in breast cancer patients who undergo neoadjuvant chemotherapy. The aims of this study are to define the appearance of HSDC sites in histopathological specimens, and to enable pathologists to recognize these sites and differentiate them from other lesions. We examined 124 breast cancer specimens in which the application of HSDCs was documented, 88 breast tissues and 36 lymph nodes, and analyzed the appearance of the clip site in these tissues. The clip site was clearly detected histologically in 79/88 (90%) of the breast specimens and in 29/36 (81%) of lymph node specimens. In most of the specimens, the HSDC site had a specific characteristic appearance of a pseudocyst, lined by layers of epithelioid histiocytes, sometimes with pseudopapillary formation, and with minimal or no fibrosis. This was the appearance in 69 of the breast specimens and in 23 of the lymph node specimens. In other specimens, scarring, scattered foamy macrophages and abundant siderophages were the predominant findings, as usually found in sites of other clips. As non-palpable breast lesions become more frequent, clips play a major role in the treatment of breast cancer, making them an important component of the communication among radiologists, surgeons, pathologists, and oncologists. HSDCs in tissues have a characteristic appearance with an epithelioid component. Pathologists should be able to recognize this finding, differentiate it from other breast lesions and include it in the pathology report.

Detectability of Hygroscopic Clips Used in Breast Cancer Surgery.

Sonographically detectable clips were introduced over the last decade. We retrospectively studied the rate and duration of sonographically detectable clip detectability in patients with breast cancer who had sonographically detectable clips inserted over a 2-year period. Nine of 26 patients had neoadjuvant chemotherapy, with all clips remaining detectable 140 to 187 days after insertion. Six of the 9 had intraoperative sonographic localization, with 1 reoperation (17%). Eleven additional patients with nonpalpable tumors and sonographically detectable clips had intraoperative sonographic localization with 1 reoperation (9%). In 1 patient, a sonographically detectable clip enabled intraoperative identification of a suspicious lymph node. There were no complications or clip migration. Sonographically detectable clips are helpful in breast cancer surgery with and without neoadjuvant chemotherapy, remaining detectable for many months and often averting preoperative localization and scheduling difficulties.

Erbin is a negative modulator of cardiac hypertrophy.

ErbB2 interacting protein (Erbin) is a widely expressed protein and participates in inhibition of several intracellular signaling pathways. Its mRNA has been found to be present in relatively high levels in the heart. However, its physiological role in the heart has not been explored. In the present work, we elucidated the role of Erbin in cardiac hypertrophy. Cardiac hypertrophy was induced in mice either by isoproterenol administration or by aortic constriction. The level of Erbin was significantly decreased in both models. Erbin(-/-) mice rapidly develop decompensated cardiac hypertrophy, and following severe pressure overload all Erbin(-/-) mice died from heart failure. Down-regulation of Erbin expression was also observed in biopsies derived from human failing hearts. It is known that Erbin inhibits Ras-mediated activation of the extracellular signal-regulated kinase (ERK) by binding to Soc-2 suppressor of clear homolog (Shoc2). Our data clearly show that ERK phosphorylation is enhanced in the heart tissues of Erbin(-/-) mice. Furthermore, we clearly demonstrate here that Erbin associates with Shoc2 in both whole hearts and in cardiomyocytes, and that in the absence of Erbin, Raf is phosphorylated and binds Shoc2, resulting in ERK phosphorylation. In conclusion, Erbin is an inhibitor of pathological cardiac hypertrophy, and this inhibition is mediated, at least in part, by modulating ERK signaling.

Myocardial mitochondrial injury induced by pulmonary exposure to particulate matter in rats.

Exposure to air pollution has been associated with acute myocardial ischemia, impaired myocardrial function, and ST-segment depression. Particulate matter (PM)-associated metals, especially vanadium and nickel, have been implicated in observed cardiovascular impairments. We aimed to assess the effect of single intratracheal pulmonary exposure to vanadium-rich respirable oil combustion PM (HP-10) on the intrinsic myocardial ischemic tolerance and mitochondrial integrity in rats. The authors subjected isolated heart tissue slices derived from saline or PM-exposed rats to low glucose low oxygen induced ischemia followed by oxygenated condition with glucose supplementation. Mitochondrial structural integrity was determined by TEM (transmission electron microscopy) and functionality by the 3-(4, 5 dimethylthiazol-2yl)-2, 5 diphenyltetrazolium bromide (MTT) assay. Rats exposed to PM exhibited no apparent inhibition of mitochondrial dehydrogenase activity in oxygenated conditions at 24 or 48 hr post-PM exposure. However, in conditions of simulated ischemia/reoxygenation, these heart slices showed a delayed but consistent and significant decrease in dehydrogenase activity compared to controls at 48 hr after exposure to PM. Electron microscopy revealed significant myocardial mitochondrial injury upon exposure to PM characterized by mitochondrial swelling and fusion. The authors conclude that exposure to soluble vanadium-rich PM induces mitochondrial functional impairment and structural abnormality, which compromises mitochondrial respiration and results in decreased tolerance to ischemia/reoxygenation in rats.

Occult cardiotoxicity--toxic effects on cardiac ischemic tolerance.

The outcome of cardiac ischemic events depends not only on the extent and duration of the ischemic stimulus but also on the myocardial intrinsic tolerance to ischemic injury. Cardiac ischemic tolerance reflects myocardial functional reserves that are not always used when the tissue is appropriately oxygenated. Ischemic tolerance is modulated by ubiquitous signal transduction pathways, transcription factors and cellular enzymes, converging on the mitochondria as the main end effector. Therefore, drugs and toxins affecting these pathways may impair cardiac ischemic tolerance without affecting myocardial integrity or function in oxygenated conditions. Such effect would not be detected by current toxicological studies but would considerably influence the outcome of ischemic events. The authors refer to such effect as "occult cardiotoxicity." In this review, the authors summarize current knowledge about main mechanisms that determine cardiac ischemic tolerance, methods to assess it, and the effects of drugs and toxins on it. The authors offer a view that low cardiac ischemic tolerance is a premorbid status and, therefore, that occult cardiotoxicity is a significant potential source of cardiac morbidity. The authors propose that toxicologic assessment of compounds would include the assessment of their effect on cardiac ischemic tolerance.

Variable Features of Juvenile Polyposis Syndrome With Gastric Involvement Among Patients With a Large Genomic Deletion of BMPR1A.

OBJECTIVES: Loss-of-function mutations of BMPR1A cause juvenile polyposis syndrome (JPS), but large genomic deletions in BMPR1A are rare, reported in few families only, and data regarding the associated phenotype are limited. METHODS: We investigated clinical features and genomic data of 7 extended seemingly unrelated families with a genomic deletion of the entire coding region of BMPR1A. We defined mutation size, mutation prevalence, and tumor pathogenesis using whole-genome sequencing, targeted genotyping, and haplotype analysis. RESULTS: Patients with JPS from 7 families of Bukharin Jewish ancestry carried a deletion of 429 kb, encompassing the BMPR1A coding sequence and 8 downstream genes. Haplotype analysis and testing controls identified this as a common founder mutation occurring in 1/124 individuals of Bukharin origin. Tumor testing did not demonstrate loss of heterozygosity. Among carriers, JPS was almost fully penetrant, but clinical features varied widely, ranging from mild to very severe, including pan-enteric polyps, gastritis, and colorectal, esophageal, and testicular cancer, and carriers with phenotypes, which would not have raised suspicion of JPS. DISCUSSION: The phenotype in this large cohort was extremely variable, although all carriers shared the same variant and the same genetic background. New observations include a preponderance of adenomatous rather than juvenile polyps, possible association with testicular cancer, and unexpected upper gastrointestinal involvement.

Incomplete methylation of a germ cell tumor (Seminoma) in a Prader-Willi male.

BACKGROUND: Prader-Willi syndrome (PWS) is a multisystem genetic disorder characterized by lack of satiety leading to morbid obesity, variable degrees of mental retardation, behavior disorders, short stature, and hypogonadism. The underlying genetic cause for PWS is an imprinting defect resulting from a lack of expression of several paternally inherited genes embedded within the 15q11.2-q13 region. Although the clinical expression of hypogonadism in PWS is variable, there are no known cases of fertility in PWS men. In this paper, we described a pure, nearly diploid seminoma in an apparently 32 year-old infertile man with PWS due to maternal uniparental disomy (UPD) on chromosome 15. The development of a germ cell tumor in this subject was an unanticipated result. The aim of this study was to explore the origin of the germ cell tumor in this PWS male patient. METHODS: To explain the origin of the germ cell tumor (seminoma) in our PWS patient we have characterized the tumor for cell morphology and tumor type by pathological examination (H&E and immuno-stainings), evaluated its karyotype by chromosomal microarray analysis and confirmed its UPD origin by haplotype analysis. In addition, DNA methylation status of the PWS- and H19- imprinting centers in wild-type and affected fibroblasts, patient derived induced pluripotent stem cells (iPSCs), and PWS seminoma were determined by bisulfite DNA colony sequencing. RESULTS: To explain the apparent contradiction between the existence of a germ cell tumor and hypogonadism we first confirmed the germ cell origin of the tumor. Next, we determined the tumor chromosomal composition, and validated the presence of a maternal UPD in all examined cell types from this patient. Finally, we characterized the maternal imprints in the PWS and H19 imprinting centers in the tumor and compared them with patient's fibroblasts and iPSCs derived from them. Unpredictably, methylation was reduced to 50% in the tumor, while preserved in the other cell types. CONCLUSION: We infer from this assay that the loss of methylation in the PWS-IC specifically in the tumor of our patient is most likely a locus-specific event resulting from imprint relaxation rather than from general resetting of the imprints throughout the genome during germ line specification.

Induction of cardiac hypertrophy by a controlled reproducible sutureless aortocaval shunt in the mouse.

Much of the understanding about the pathophysiological responses to chronic cardiac overload has been gained by the use of rat and dog models of aortocaval fistula (ACF). The use of a similar model in genetically manipulated mice may further elucidate the molecular mechanisms in these responses. The only reports about ACF in mice to date have applied a needle puncture to create the ACF, which may result in an uncontrolled and irreproducible size of the shunt, and require several weeks to induce the characteristic cardiac changes. In order to obtain a more consistent approach to characterize this mode of cardiac hyperfunction, we present a surgical murine model of ACF that results in rapid progression of the typical systemic and cardiac changes. A sutureless side-to-side infrarenal surgical anastomosis of 0.6-0.8 mm in diameter was created between the abdominal aorta and inferior vena cava in ICR (Institute of Cancer Research) mice. Six to 7 days later, significant cardiac hypertrophy developed. The heart/body weight ratio increased from 0.45 +/- 0.02% in control mice to 0.77 +/- 0.03% in mice with ACF (p < .003). The dry heart weight ratio increased from 0.099 +/- 0.0033% to 0.13 +/- 0.008% (p < .006). The ACF dramatically induced the atrial and ventricular expression of atrial natriuretic factor mRNA, and increased the total cardiac content of endothelin-1 (162.5 +/- 50.6 vs. 83.9 +/- 9.0 pg). Mean arterial pressure in anesthetized mice with ACF decreased from 69.8 +/- 4.9 to 54.8 +/- 5.5 mm Hg (p < .025). Urinary sodium excretion returned to preoperative levels several days following surgery. These results demonstrate that cardiac hypertrophy could be rapidly and reproducibly achieved in mice by the placement of a surgical ACF. This model, when applied in genetically manipulated mice, may be a valuable tool for functional genomic studies about the pathogenesis of cardiac hypertrophy and heart failure.

FHL2 switches MITF from activator to repressor of Erbin expression during cardiac hypertrophy.

BACKGROUND: Congestive heart failure (CHF) is a significant health care burden in developed countries. However, the molecular events leading from cardiac hypertrophy to CHF are unclear and preventive therapeutic approaches are limited. We have previously described that microphthalmia-associated transcription factor (MITF) is a key regulator of cardiac hypertrophy, but its cardiac targets are still uncharacterized. METHODS AND RESULTS: Gene array analysis of hearts from MITF-mutated mice indicated that ErbB2 interacting protein (Erbin) is a candidate target gene for MITF. We have recently demonstrated that Erbin is decreased in human heart failure and plays a role as a negative modulator of pathological cardiac hypertrophy. Here we show that Erbin expression is regulated by MITF. Under basal conditions MITF activates Erbin expression by direct binding to its promoter. However, under ß-adrenergic stimulation Erbin expression is decreased only in wild type mice, but not in MITF-mutated mice. Yeast two-hybrid screening, using MITF as bait, identified an interaction with the cardiac-predominant four-and-a-half LIM domain protein 2 (FHL2), which was confirmed by co-immunoprecipitation in both mouse and human hearts. Upon ß-adrenergic stimulation, FHL2 and MITF bind Erbin promoter as a complex and repress MITF-directed Erbin expression. Overexpression of FHL2 alone had no effect on Erbin expression, but in the presence of MITF, Erbin expression was decreased. FHL2-MITF association was also increased in biopsies of heart failure patients. CONCLUSION: MITF unexpectedly regulates both the activation and the repression of Erbin expression. This ligand mediated fine tuning of its gene expression could be an important mechanism in the process of cardiac hypertrophy and heart failure.

Rapid proliferation of prostatic epithelial cells in spontaneously hypertensive rats: a model of spontaneous hypertension and prostate hyperplasia.

Spontaneously hypertensive rats (SHRs), a commonly used model of genetic hypertension, exhibit features of glandular hyperplasia of the ventral prostate, including the narrowing of acini with epithelial protrusions into the lumen and the piling up of epithelial cells. These rats also have frequent urinary voiding. In order to define the fundamental processes that lead to prostatic hyperplasia in SHRs, we compared the proliferation rate of their prostatic epithelial cells (PECs) in primary culture and in vivo to that of Wistar-Kyoto rats (WKYs), their normotensive controls. In vitro, primary cultures of SHR PECs had a shorter doubling time than those of WKY (3.3 vs 8.0 days) and showed higher levels of bromodeoxyuridine (BrdU) incorporation into DNA. In vivo, the BrdU incorporation seen 48 hours following injection was observed primarily in areas of epithelial piling up, which are seen in SHRs but not in WKYs. We concluded that prostate hyperplasia in SHRs results from a genuine increase in the proliferation rate of PECs and that this rapid proliferation is a fundamental feature of SHR PECs, maintained both in vivo and in vitro. Thus, SHRs can serve as a model for glandular hyperplasia of the prostate, resulting from a genetic tendency for an increased rate of cell proliferation.

Scanning electron microscopic analysis of intramyocellular lipid droplets in an animal model of type 2 diabetes.

OBJECTIVE: To evaluate the accumulation pattern of intramyocellular lipids (IMCLs) in striated muscle during the development and progression of diabetes, using a novel scanning electron microscopic method. METHODS AND PROCEDURES: Hyperglycemia was induced by feeding diabetes-prone (DP) Psammomys obesus a high-energy (HE) diet. Lipid accumulation within gastrocnemius muscle fibers was assessed in formalin-fixed muscle samples during the development of hyperglycemia using high resolution imaging in a scanning electron microscope. We evaluated the temporal relationship between changes in IMCL quantity and morphology and the altered glucose metabolism and assessed the effect of reversal of hyperglycemia on IMCL level and morphology. Diabetes-resistant (DR) P. obesus served as controls. RESULTS: Lipid accumulation in the muscle fibers of DP animals was increased with the development of hyperglycemia. This was characterized by increased lipid density as well as by an abundance of large lipid droplets. Reversal of the phenotype resulted in the disappearance of large lipid droplets. The IMCL level and the distribution of lipid droplet size were similar in muscles of both the normoglycemic DR and DP animals, with an abundance of small lipid droplets. This profile was changed following a HE diet only in the DP animals. DISCUSSION: Lipid accumulation in the muscle of P. obesus during the development of hyperglycemia is characterized by increased quantity and accumulation of large lipid droplets. These changes were reversible upon normalization of blood glucose. The evaluated methodology is a useful tool for the study of the dynamics of lipid accumulation in different metabolic conditions.

Occult cardiotoxicity: subtoxic dosage of Bis(2-chloroethoxy)methane impairs cardiac response to simulated ischemic injury.

The effect of Bis(2-chloroethoxy)methane (CEM) on myocardial response to ischemia was tested in rats. CEM was dermally applied for 3 days to F344/N male rats, at 0, 100, 400, or 600 mg/kg/d. Subsequently, left ventricular sections were prepared from each rat heart. Part of the sections from each heart were exposed to 90 minutes of simulated ischemia, followed by 90 minutes of reoxygenation. The rest of the sections were continuously oxygenated. Mitochondrial activity was assessed in the sections by the MTT colorimetric assay, reflecting dehydrogenases redox activity. Myocardial toxicity occurred in response to 400 and 600 mg/kg, characterized by myofiber vacuoles, necrosis, and mononuclear infiltrates. The latter dose was lethal. In sections from rats treated with 400 mg/kg CEM, redox activity was decreased by 21% (p<0.01) in oxygenated conditions and by 45% (p<0.01) in ischemia-reoxygenation, compared to controls. Hearts of rats treated with 100 mg/kg/d CEM showed normal histology. Their mitochondrial activity did not differ from that of untreated rat hearts in oxygenated conditions. However, in ischemia-reoxygenation, their redox activity was significantly lower (by 46%, p<0.01) than that of untreated rat hearts. These results demonstrate that subtoxic dosage of a cardiotoxic agent may cause occult cardiotoxicity, reflected by impaired response to ischemia.

Preoperative lymphatic mapping does not predict the number of axillary sentinel lymph nodes identified during surgery in breast cancer patients.

Sentinel lymph node biopsy (SLNB) has become the standard of care in most centers for axillary staging in patients with early breast cancer. Multiple radioactive nodes are often identified at surgery. The finding of multiple sentinel lymph nodes (SLNs) has been shown to be associated with lower rates of false-negative results in the SLNB procedure, hence the importance of removing and examining all SLNs. Often preoperative lymphatic mapping (PLM) is performed prior to surgery. In this study we examined whether the exact number of SLNs identified during surgery can be accurately predicted by PLM. During the years 2001-2004, 155 patients underwent both PLM and a SLNB in our breast unit. During surgery, an attempt was made to remove all radioactive nodes. The number of axillary radioactive foci found on PLM was compared with the number of radioactive nodes identified during surgery. The average number of sentinel nodes harvested was 2.3 (range 1-9). The average number of radioactive foci identified on PLM was 1.8 (range 0-5). Of the 155 patients, the number of sentinel nodes retrieved in surgery was greater than that found in preoperative mapping in 65 patients (41.9%), equal to that found in preoperative mapping in 60 patients (38.7%), and less than that found in preoperative mapping in 30 patients (19.4%). Thus in most patients, the number of SLNs found on PLM did not reflect the number of SLNs found intraoperatively. Therefore, even when the number of nodes identified on PLM has been reached in surgery, a meticulous search for additional nodes should still be carried out. The number of hot spots in preoperative mapping should serve as a rough indicator of the smallest number of nodes the surgeon should attempt to resect, but not the exact number of nodes expected to be found.

Intraoperative palpation for clinically suspicious axillary sentinel lymph nodes reduces the false-negative rate of sentinel lymph node biopsy in breast cancer.

Axillary sentinel lymph node biopsy (SLNB) is widely used to identify the first lymph node draining breast tumors. When the sentinel lymph node is free of metastasis, axillary dissection is avoided because the rest of the nodes are expected to be negative as well. A false-negative rate of 5% is considered acceptable. In the case of a false-negative SLNB, adjuvant local and systemic treatments might be suboptimal. We assessed the effect of intraoperative axillary palpation for clinically suspicious lymph nodes that are not otherwise detected by radioactive tracer or blue dye on the false-negative rate of SLNB in breast cancer patients. Our prospective database of patients having surgery for primary invasive breast cancer and who had a SLNB from 2000 to 2004 was reviewed. Only patients with clinically negative nodes preoperatively were included. The procedure included preoperative injection of radiotracer, with dye injection as backup, and intraoperative palpation of the axilla for suspicious lymph nodes that were not radioactive or blue. Of the 290 patients, 89 (30.7%) had sentinel node involvement by tumor. Seven patients had clinically suspicious nodes identified solely by palpation and not by tracer, in addition to sentinel lymph nodes detected by tracer. In five of the seven patients, the nodes harbored metastasis. In four of these five patients (4.5% of the 89 patients with axillary involvement), the palpable nodes were the only ones involved. A generous axillary incision and systematic palpation of the axilla reduces the false-negative rate and should be a part of the SLNB procedure.

The "Sentinel Chain": a new concept for prediction of axillary node status in breast cancer patients.

BACKGROUND AND OBJECTIVES: More than half the breast cancer patients with positive sentinel lymph nodes (SLN) do not harbor additional metastases in non-sentinel nodes (NSN). The aim of this study was to identify a subgroup of patients with positive SLNs and negative NSNs, on the basis of tumor involvement patterns in multiple radioactive nodes. METHODS: Between 2000 and 2004, 290 patients with primary invasive breast cancer and clinically negative axillary nodes had a SLN biopsy in our breast unit. Radiotracer was identified intraoperatively in the axilla. All radioactive nodes were removed and radioactivity was measured in each node extracorporeally. Nodes were ranked according to radioactivity, constituting a "Sentinel Chain", and the histopathological status of each node was reported. The different metastatic involvement patterns of the Sentinel Chain were correlated with the metastatic status of the NSNs after axillary dissection. Information was charted in a prospective database. RESULTS: Of 290 patients, 216 (74.5%) had multiple radioactive nodes. Ninety patients (31%) had SLN metastases. Fifty patients had multiple ranked radioactive nodes and positive SLNs. Twenty-five of these patients had a sequential involvement pattern, with tumor-bearing high radioactivity nodes, and uninvolved low-radioactivity nodes. In the 23 of these 25 patients who had axillary dissection, NSN involvement was detected in only one patient (4.3%), whereas in 24 patients with other involvement patterns of the Sentinel Chain, NSN involvement reached 54.2% (p<0.001). CONCLUSION: Tumor-free status of NSN may be predicted using the Sentinel Chain concept in some breast cancer patients with positive SLNs.