The usefulness of pleural fluid presepsin, C-reactive protein, and procalcitonin in distinguishing different causes of pleural effusions.

BACKGROUND: We aimed to determine the presepsin concentration in pleural fluid from patients with pleural effusions of different aetiologies and to compare its diagnostic value with that of pleural fluid C-reactive protein (CRP) and procalcitonin (PCT). METHODS: We enrolled 132 patients with pleural effusion who underwent diagnostic evaluation, and we classified them into six categories: empyema, parapneumonic effusion, tuberculous effusion, malignant effusion, paramalignant effusion, and transudate effusion. Additionally, all pleural effusions were categorised as infectious or non-infectious effusions. RESULTS: Receiver operating characteristic analysis was used to evaluate diagnostic performance. When diagnosing empyema, the marker with the highest sensitivity was pleural fluid presepsin (cut-off: 754 pg/mL; sensitivity: 90.9%, specificity: 74.4%) and that with the highest specificity was pleural fluid CRP (cut-off: 4.91 mg/dL; sensitivity: 63.6%, specificity: 89.3%). Pleural fluid PCT tended to be lower in patients with empyema than in those with parapneumonic effusion, but this was not useful for the diagnosis of empyema. When diagnosing infectious pleural effusion, a combination of pleural fluid CRP (cut-off: 2.59 mg/dL) and presepsin (cut-off: 680 pg/mL) produced the highest diagnostic accuracy (83.3%). CONCLUSIONS: Pleural fluid presepsin was found at high levels in patients with empyema and parapneumonic effusion. This pattern closely resembles the previously reported pattern of pleural fluid CRP. Some combinations of pleural fluid inflammatory markers may be more clinically useful than these markers in isolation.

Hepatocyte growth factor produced in lung fibroblasts enhances non-small cell lung cancer cell survival and tumor progression.

BACKGROUND: The influence of lung fibroblasts on lung cancer progression is not fully understood. METHODS: Lung fibroblasts (HFL1, MRC5, and IMR90 cells) and non-small cell lung cancer (NSCLC)-derived cell lines (A549, EBC1, and HI1017) were cultured under serum-free conditions, and the resulting culture media were designated "cell-conditioned media". Cell survival (viability) was assessed by WST-1 assay. Concentrations of hepatocyte growth factor (HGF) were measured by ELISA. The BALB/c-nu mouse strain was used for the xenograft model. RESULTS: Lung fibroblast-conditioned media enhanced the survival of the three NSCLC cell lines tested. HGF was produced to a greater extent by lung fibroblasts than NSCLC cells. Exogenous HGF enhanced the survival of NSCLC cells. Either an anti-HGF neutralizing antibody or the Met inhibitor PHA-665752 inhibited the fibroblast-conditioned media-enhanced survival of NSCLC cells. The co-inoculation of mice with NSCLC cells and fibroblasts enhanced tumorigenicity and tumor progression in a mouse xenograft model. PHA-665752 significantly inhibited tumor progression that occurred after the co-inoculation of NSCLC cells and fibroblasts. In addition, HGF production by fibroblasts was stimulated by NSCLC cells. CONCLUSIONS: The current study provides evidence for an interaction between fibroblasts and NSCLC cells via the HGF/Met signaling pathway, which affects NSCLC cell survival and tumor progression. These findings may contribute to the development of anti-cancer-associated fibroblast therapeutic strategies. TRIAL REGISTRATION: No trial registration is required because this study is not a clinical trial. This study does not include any participants or patients.

Phanerochaete sordida as a cause of pulmonary nodule in an immunocompromised patient: a case report.

BACKGROUND: Phanerochaete sordida is a species of wood rotting fungus, which can degrade lignin, cellulose and hemicellulose contained in wood and other hard-to-biodegrade organic substances. However, to date, there have been no other reports demonstrating that P. sordida can infect humans. CASE PRESENTATION: A 66-year-old Japanese man presented for a mass increasing in size on his left thigh. He had been suffering from rheumatoid arthritis for 18 years and chronic obstructive pulmonary disease for 20 years, for which he was being treated with 5 mg/day prednisolone and 8 mg/week methotrexate. The mass resection was performed two months later, and was diagnosed as malignant fibrous histiocytosis. However, a computed tomography examination for tumor recurrence after surgery showed a newly emergent pulmonary nodule. We therefore decided to resect the nodule by thoracoscopic procedure. Histopathological examination of the excised specimen showed that the lesion was a granuloma, with necrotic tissue and clumping of Aspergillus-like hyphae. Therefore, the nodule was diagnosed as a fungal infection and tissue specimens were cultured microbiologically. However, fungal growth was not observed. We consequently performed genetic analysis using a broad-range polymerase chain reaction. The 28S rRNA sequence demonstrated 100% homology with P. sordida using the NCBI BLAST program against the GenBank DNA databases. CONCLUSIONS: Using broad-range polymerase chain reaction, we identified P. sordida as the causative agent of a pulmonary nodule. These findings indicate that P. sordida may be an additional opportunistic causative organism of pulmonary infection in immunocompromised patients.

Confluence-dependent resistance to cisplatin in lung cancer cells is regulated by transforming growth factor-beta.

PURPOSE OF THE STUDY: Confluence-dependent resistance (CDR) is a phenomenon in which the efficacy of anti-cancer agents decreases when cell density increases. CDR in lung cancer has never been reported. The purpose of this study is to investigate if CDR can occur in NSCLC cells and to find a role for transforming growth factor (TGF)-ß as a mechanism of CDR. MATERIALS AND METHODS: Non-small cell lung cancer (NSCLC) cell lines A549 and H2228 were exposed to cisplatin in a variety of cell density conditions. RNA interference targeting TGF-ß receptor I was performed to silence the TGF-ß pathway. RESULTS: CDR to cisplatin was induced in NSCLC cells, whereas CDR to crizotinib, an inhibitor of activin receptor-like kinase, was not observed. During confluent conditions, the TGF-ß1 concentration in the culture medium was the highest. Exogenous TGF-ß1 inhibited cell proliferation and reduced sensitivity to cisplatin. Inhibition of the TGF-ß pathway increased in terms of sensitivity to cisplatin at confluency. CONCLUSIONS: CDR to cisplatin can occur in NSCLC cells, and the TGF-ß pathway is associated with the regulation of CDR.

A case of catastrophic antiphospholipid syndrome, which presented an acute interstitial pneumonia-like image on chest CT scan.

We report the case of catastrophic antiphospholipid syndrome (CAPS) complicated with mixed connective tissue disease (MCTD). A female patient was diagnosed with acute interstitial pneumonia (AIP) with MCTD by chest CT scan. Corticosteroid therapy was refractory for lung involvement, and she died due to acute respiratory failure. The autopsy revealed that AIP was compatible with lung involvement of CAPS. We therefore suggest that chest CT might reveal AIP-like findings in CAPS patients whose condition is complicated with pulmonary manifestations.

Calmodulin antagonists induce cell cycle arrest and apoptosis in vitro and inhibit tumor growth in vivo in human multiple myeloma.

BACKGROUND: Human multiple myeloma (MM) is an incurable hematological malignancy for which novel therapeutic agents are needed. Calmodulin (CaM) antagonists have been reported to induce apoptosis and inhibit tumor cell invasion and metastasis in various tumor models. However, the antitumor effects of CaM antagonists on MM are poorly understood. In this study, we investigated the antitumor effects of naphthalenesulfonamide derivative selective CaM antagonists W-7 and W-13 on MM cell lines both in vitro and in vivo. METHODS: The proliferative ability was analyzed by the WST-8 assay. Cell cycle was evaluated by flow cytometry after staining of cells with PI. Apoptosis was quantified by flow cytometry after double-staining of cells by Annexin-V/PI. Molecular changes of cell cycle and apoptosis were determined by Western blot. Intracellular calcium levels and mitochondrial membrane potentials were determined using Fluo-4/AM dye and JC-10 dye, respectively. Moreover, we examined the in vivo anti-MM effects of CaM antagonists using a murine xenograft model of the human MM cell line. RESULTS: Treatment with W-7 and W-13 resulted in the dose-dependent inhibition of cell proliferation in various MM cell lines. W-7 and W-13 induced G1 phase cell cycle arrest by downregulating cyclins and upregulating p21cip1. In addition, W-7 and W-13 induced apoptosis via caspase activation; this occurred partly through the elevation of intracellular calcium levels and mitochondrial membrane potential depolarization and through inhibition of the STAT3 phosphorylation and subsequent downregulation of Mcl-1 protein. In tumor xenograft mouse models, tumor growth rates in CaM antagonist-treated groups were significantly reduced compared with those in the vehicle-treated groups. CONCLUSIONS: Our results demonstrate that CaM antagonists induce cell cycle arrest, induce apoptosis via caspase activation, and inhibit tumor growth in a murine MM model and raise the possibility that inhibition of CaM might be a useful therapeutic strategy for the treatment of MM.

Potentiated activation of VLA-4 and VLA-5 accelerates proplatelet-like formation.

Fibronectin (FN) plays important roles in the proliferation, differentiation, and maintenance of megakaryocytic-lineage cells through FN receptors. However, substantial role of FN receptors and their functional assignment in proplatelet-like formation (PPF) of megakaryocytes are not yet fully understood. Herein, we investigated the effects of FN receptors on PPF using the CHRF-288 human megakaryoblastic cell line, which expresses VLA-4 and VLA-5 as FN receptors. FN and phorbol 12-myristate 13-acetate (PMA) were essential for inducing PPF in CHRF-288 cells. Blocking experiments using anti-ß1-integrin monoclonal antibodies indicated that the adhesive interaction with FN via VLA-4 and VLA-5 were required for PPF. PPF induced by FN plus PMA was accelerated when CHRF-288 cells were enforced adhering to FN by TNIIIA2, a peptide derived from tenascin-C, which we recently found to induce ß1-integrin activation. Adhesion to FN enhanced PMA-stimulated activation of extracellular signal-regulated protein kinase 1 (ERK1)/2 and enforced adhesion to FN via VLA-4 and VLA-5 by TNIIIA2-accelerated activation of ERK1/2 with FN plus PMA. However, c-Jun amino-terminal kinase 1 (JNK1), p38, and phosphoinositide-3 kinase (PI3K)/Akt were not stimulated by FN plus PMA, even with TNIIIA2. Thus, the enhanced activation of ERK1/2 by FN, PMA plus TNIIIA2 was responsible for acceleration of PPF with FN plus PMA.

[Pulmonary Langerhans cell histiocytosis in a non-smoking Japanese woman].

A 44-year-old Japanese woman was admitted to our hospital because of dry cough and dyspnea on exertion. She had never smoked. She had been passively exposed to smoking by her husband and co-workers from the age of 21 (1984) to 33 (1996). She had previously developed pneumothorax twice, in 1985. On admission, computed tomography (CT) of the chest showed reticulonodular opacities predominant in bilateral upper lung fields, and pulmonary function tests revealed a decrease in vital capacity. The differential diagnoses were sarcoidosis, idiopathic pulmonary fibrosis and pulmonary Langerhans cell histiocytosis (PLCH). Video-assisted thoracic surgery was performed to make a definitive diagnosis. A histological specimen revealed the presence of CD1a-positive Langerhans cells in bronchiolocentric nodular lesions, leading to a diagnosis of PLCH. She was given 0.5 mg/kg bodyweight/ day oral prednisolone. Her symptoms disappeared with steroid maintenance therapy, and her vital capacity on pulmonary function testing was prevented from further deterioration. Based on the pathogenesis of PLCH, this case suggested that not only active smoking, but also passive smoking, played an important role in the development of PLCH.

Asthma mortality based on death certificates: A demographic survey in Kagawa, Japan.

BACKGROUND: We aimed to determine the reasons for the high rate of asthma mortality in Kagawa Prefecture, Japan, by analyzing death certificates. METHODS: We analyzed the death certificates between 2009 and 2011 in a demographic survey. Of 1187 patients with documented disease names suggesting bronchial asthma, analysis was performed on 103 patients in whom the cause of death was classified as asthma based on ICD-10 Codes. The patients were then classified into the following 4 groups: asthma death, asthma-related death, non-asthma death, and indistinguishable death. Based on this classification, consistency between ICD-10-based asthma death and asthma/asthma-related deaths was examined for each age group as well as for the site of death. RESULTS: Of 103 asthma deaths based on the ICD-10 classification, 30 (29%) were classified as asthma death, 44 (43%) as asthma-related death, 16 (16%) as non-asthma death, and 13 (13%) as indistinguishable death. Asthma death based on our classification correlated with that of ICD-10-based classification as a cause of death in patients younger than the median age (87 years), but correlation was not observed in patients aged older than 87 years. Deaths occurred outside the hospital in 45% of patients, and many ICD-10-based deaths reported at nursing homes and geriatric health care facilities were classified as non-asthma deaths in this survey. CONCLUSION: Re-examination of the death certificate revealed that asthma deaths were reported incorrectly on the death certificates of elderly patients who died outside the hospital.

Full-length cytokeratin 8 is released and circulates in patients with non-small cell lung cancer.

BACKGROUND/AIM: Cytokeratin 8 (CK8) is a type II intermediate filament protein that is persistently expressed in most epithelial malignancies. Circulating CK-related polypeptides have commonly been used as tumor markers. While apoptosis is a mechanism of CK release, the molecular nature of circulating CKs is poorly understood. The aim is to clarify the dynamics of CK8 during apoptosis in vitro and the nature of circulating CK8 in patients with lung cancer. METHODS: Extracellular release of CK8 was examined using A549 human non-small cell lung cancer (NSCLC) cells after apoptosis induction by etoposide. Serum samples from NSCLC patients were examined for circulating CK8 by ELISA (n = 60) and by immunoprecipitation (n = 9). RESULTS: CK8 is released predominantly in full length from A549 cells undergoing apoptosis and is resistant to intracellular cleavage by caspases, unlike type I CK18, which is readily cleaved during apoptosis. Full-length CK8 is shown to constitute a considerable fraction of circulating CK8 in the serum of lung cancer patients. CONCLUSION: Apoptosis causes extracellular release of full-length CK8 in NSCLC cells. CK8 circulates predominantly in full length in patients with NSCLC, illustrating the fundamental differences in protein processing between type I and type II CKs.

Positron emission tomography-positive squalene-induced lipoid pneumonia confirmed by gas chromatography-mass spectrometry of bronchoalveolar lavage fluid.

Squalene is a type of oil obtained from shark liver. We describe a 76-year-old man diagnosed with chronic exogenous lipoid pneumonia due to squalene. A chest CT scan revealed pulmonary consolidation with ground-glass opacities in the right upper lobe. Positron emission tomography (PET) revealed significant uptake of 2-deoxy-2-F-fluoro-d-glucose (FDG) and 3'-deoxy-3'-F-fluorothymidine (FLT). Bronchoalveolar lavage (BAL) fluid contained many lipid-laden macrophages, and a transbronchial lung biopsy specimen showed clusters of foamy macrophages in alveolar spaces and granulomatous lesions. In addition, the presence of squalene in the BAL fluid was confirmed by gas chromatography-mass spectrometry, leading to a diagnosis of squalene-induced lipoid pneumonia. To the best of our knowledge, this is the first report of squalene-induced lipoid pneumonia in which squalene itself was successfully detected. This case also suggests the possibility that lipoid pneumonia shows significant uptake in FDG-PET and FLT-PET.

Transforming Growth Factor-Beta Produced by Non-small Cell Lung Cancer Cells Contributes to Lung Fibroblast Contractile Phenotype.

BACKGROUND/AIM: Fibroblasts can alter the extracellular matrix (ECM), contributing to cancer progression by providing a scaffold for cancer cells. The influence of lung cancer cells (LCCs) on lung fibroblast-mediated ECM alteration is not well understood. MATERIALS AND METHODS: After incubation in serum-free medium, LCC- or fibroblast-conditioned media were collected. The ECM alteration was assessed by collagen gel contraction assay. RESULTS: Both LCC-conditioned medium and exogenous transforming growth factor (TGF)-ß1 increased collagen gel contraction by lung fibroblasts. TGF-ß1 was produced in LCC-conditioned media at approximately 2 ng/ml. SB431542, a specific TGF-ß receptor kinase inhibitor, partially inhibited the collagen gel contraction that had been increased by LCC-conditioned media. Lung fibroblast-conditioned medium stimulated TGF-ß1 production from LCCs, whereas LCC-conditioned medium decreased fibroblast survival and α-smooth muscle actin expression by fibroblasts. CONCLUSION: Interaction between LCCs and lung fibroblasts through TGF-ß signaling induces fibroblasts to assume the contractile phenotype and may contribute to cancer progression.

Lemongrass essential oil and citral inhibit Src/Stat3 activity and suppress the proliferation/survival of small-cell lung cancer cells, alone or in combination with chemotherapeutic agents.

Small-cell lung cancer (SCLC) is intractable due to its high propensity for relapse. Novel agents are thus needed for SCLC treatment. Lemongrass essential oil (LG-EO) and its major constituent, citral, have been reported to inhibit the proliferation and survival of several types of cancer cells. However, the precise mechanisms through which LG-EO and citral exert their effects on SCLC cells have not been fully elucidated. SCLC cells express Src and have high levels of Src-tyrosine kinase (Src-TK) activity. In most SCLC cell lines, constitutive phosphorylation of Stat3(Y705), which is essential for its activation, has been detected. Src-TK can phosphorylate Stat3(Y705), and activated Stat3 promotes the expression of the anti-apoptotic factors Bcl-xL and Mcl-1. In the present study, LG-EO and citral prevented Src-TK from phosphorylating Stat3(Y705), resulting in decreased Bcl-xL and Mcl-1 expression, in turn suppressing the proliferation/survival of SCLC cells. To confirm these findings, the wild-type-src gene was transfected into the LU135 SCLC cell line (LU135­wt-src), in which Src and activated phospho-Stat3(Y705) were overexpressed. The suppression of cell proliferation and the induction of apoptosis by treatment with LG-EO or citral were significantly attenuated in the LU135-wt-src cells compared with the control LU135-mock cells. The signal transducer and activator of transcription 3 (Stat3) signaling pathway is also associated with intrinsic drug resistance. LU135-wt-src cells were significantly resistant to conventional chemotherapeutic agents compared with LU135-mock cells. The combined effects of citral and each conventional chemotherapeutic agent on SCLC cells were also evaluated. The combination treatment exerted additive or more prominent effects on LU135-wt-src, LU165 and MN1112 cells, which are relatively chemoresistant SCLC cells. These findings suggest that either LG-EO or citral, alone or in combination with chemotherapeutic agents, may be a novel therapeutic option for SCLC patients.

Compensation of type I and type II cytokeratin pools in lung cancer.

Cytokeratins (CKs) constitute the largest family of intermediate filament proteins, and are subdivided into type I (CK9-CK23) and type II (CK1-CK8) subclasses. CK19 is expressed in non-small cell lung cancer (NSCLC), and serum CK19 fragment (referred to as CYFRA21-1) is one of the tumor markers used in diagnosing NSCLC. Type I and type II CKs have been shown to form obligate 1:1 heteropolymers, suggesting that dynamic changes must occur in the expression levels of CK pools when one CK is suppressed. However, the absolute levels of CK expression and their dynamic changes have not been fully evaluated. Therefore, we quantitatively determined CK expression levels in NSCLC cell lines, and evaluated the rate of change of CK expression levels after RNA interference targeting of single CKs. In NSCLC cells, type I CK18 and type II CK8 are the dominant CKs, with absolute expression levels of 12-77pmol/10(6)cells, while the expression patterns of the CKs vary among cell lines. Moderate suppression of a single dominant CK caused downregulation in CKs of the complementary type, and upregulation of other CKs of the same type. In contrast, severe suppression of a single dominant CK caused almost complete suppression of all CKs. In addition, introduction of CK19 led to resistance to CK degradation by CK18 suppression. These data suggest the presence of a critical threshold expression level for a dominant CK and a role for CK19 in the compensation of type I and type II CK pools in NSCLC.

Preventive effects of low-dose dexamethasone for delayed adverse events induced by carboplatin-based combination chemotherapy.

We performed a retrospective study to examine the protective effect of low-dose dexamethasone (DEX) on delayed adverse events induced by carboplatin (CBDCA)-based combination chemotherapy in patients with thoracic tumors. Low-dose DEX (4-8 mg/day) was administered on day 1 and after, in addition to a serotonin 5-HT3 receptor antagonist. The acute adverse events (day 1) were well controlled in the patients with or without co-treatment of DEX. On the other hand, the delayed nausea, emesis, anorexia, and fatigue after day 2 failed to be controlled by 5-HT3 antagonist alone. Co-treatment with DEX significantly suppressed the grade of the delayed adverse events during days 2-10. The mean ratio of complete protection during days 2-10 were significantly higher in the DEX-treated group compared with the non-DEX-treated group. These results reveal that low-dose DEX is a clinically effective treatment for the prevention of delayed adverse events induced by CBDCA-based combination chemotherapy.

[Hand-foot syndrome associated with uracil/tegafur and docetaxel in a patient with lung cancer].

A 30-year-old woman given a diagnosis of stage IV lung adenocarcinoma, was admitted to our hospital because of chest pain due to pleuritis carcinomatosa. She had taken uracil/tegafur (UFT) 600mg orally every day from September 2004. Uracil/tegafur was stopped in December 10, 2005, and docetaxel (taxotere) 50mg/m2 was given in December 12, 2005. Seven days after treatment with docetaxel she developed erythema and spontaneous pain of the palms and fingers of both hands and soles of both feet. The erythema increased gradually, and 10 days after docetaxel infusion she could not walk due to severe pain. After improvement of the painful erythema, desquamation of fingers of both hands and the soles of both feet occurred. She was diagnosed with hand-foot syndrome. Although the same amount of docetaxel was given later, hand-foot syndrome was not seen. Therefore it was suggested that both uracil/tegafur and docetaxel induced hand-foot syndrome. Fluoropyrimidines and taxanes have been reported as common anti-cancer drugs that lead to hand-foot syndrome. Since these drugs play a crucial role in lung cancer treatment, we need to pay attention to hand-foot syndrome. A sufficient off-drug period is required in the sequential usage of fluoropyrimidines and taxanes.

Fibronectin and Hepatocyte Growth Factor Produced by Lung Fibroblasts Augment Migration and Invasion of Malignant Pleural Mesothelioma Cells.

BACKGROUND: The interaction between fibroblasts and malignant pleural mesothelioma (MPM) cells is not well understood. MATERIALS AND METHODS: Lung fibroblasts (HFL1, MRC5 and IMR90) and MPM cells (H28, H226 and H2052) were cultured under serum-free conditions and the resulting culture media were collected. Migration and invasion of MPM cells were assessed by chemotaxis and Matrigel assays, respectively. RESULTS: Lung fibroblast-derived media enhanced the migration and invasion of the three tested MPM cell lines. Fibronectin and hepatocyte growth factor (HGF) were produced by lung fibroblasts. Exogenous fibronectin and HGF also enhanced the migration and invasion of the three MPM cells, respectively. Neutralizing anti-HGF antibody inhibited the invasion of H28 cells enhanced by fibroblast-derived media. In addition, the production of fibronectin and HGF was stimulated by MPM cell-derived media. CONCLUSION: The current study provides additional evidence that might contribute to the development of antitumor-associated fibroblast therapeutic strategies.

Infective endocarditis and infected aneurysm caused by Streptococcus dysgalactiae subsp. equisimilis: a case report.

Endocarditis caused by Streptococcus dysgalactiae subsp. equisimilis (SDSE) is rare. Infected aneurysm is one of the most serious complications of infective endocarditis. However, no reports have described SDSE-related infected aneurysm. We herein report a successfully treated case of SDSE-associated infective endocarditis with an infected aneurysm.

Tumor Spread Through Air Spaces Is an Independent Predictor of Recurrence-free Survival in Patients With Resected Lung Squamous Cell Carcinoma.

Tumor spread through air spaces (STAS) is a newly recognized pattern of invasion in lung adenocarcinoma. However, clinical significance of STAS has not yet been characterized in lung squamous cell carcinoma. In this study, we investigated whether STAS could determine clinical outcome in Japanese patients with lung squamous cell carcinoma. We reviewed tumor slides from surgically resected lung squamous cell carcinomas (n=216). STAS was defined as tumor cells within air spaces in the lung parenchyma beyond the edge of the main tumor. Tumors were evaluated for histologic subtypes, tumor budding, and nuclear diameter. Recurrence-free survival (RFS) was analyzed using the log-rank test and the Cox proportional hazards model. Tumor STAS was observed in 87 patients (40%), increasing incidence with lymph node metastasis (P=0.037), higher pathologic stage (P=0.026), and lymphatic invasion (P=0.033). All cases with STAS showed a solid nest pattern. The 5-year RFS for patients with STAS was significantly lower than it was for patients without STAS in all patients (P=0.001) and in stage I patients (n=134; P=0.041). On multivariate analysis, STAS was an independent prognostic factor of a worse RFS (hazard ratio=1.61; P=0.023). Patients with STAS had a significantly increased risk of developing locoregional and distant recurrences (P=0.012 and 0.001, respectively). We found that tumor STAS was an independent predictor of RFS in patients with resected lung squamous cell carcinoma, and it was associated with aggressive tumor behavior.