Maintenance therapy has emerged as a novel therapeutic paradigm for advanced non-small-cell lung cancer (NSCLC). Maintenance therapy that aims to sustain a clinically favorable state after first-line chemotherapy has two strategies. Switch maintenance therapy entails switching to a new and non-cross-resistant agent in an alternating or sequential manner, on completion of first-line chemotherapy. Continuous maintenance therapy keeps ongoing administration of a component of the current regimen after four to six cycles of chemotherapy, if there is a stable disease, or better response. Both maintenance therapies can be continued, until disease progression. The potential evidence regarding maintenance therapy includes providing the opportunity to receive additional treatment, through sustaining tumor shrinkage, and delayed emergence of tumor-related symptom. Thus far, debates over the parameters used to predict the effectiveness of maintenance therapy, financial burden, and uncertainty of improving the quality of life exist. Despite many debates, maintenance therapy, which is currently recommended, has been disclosed to be beneficial.

Non-small cell lung cancer harboring epidermal growth factor receptor (EGFR) sensitizing mutations has a distinct disease entity. Patients with this cancer have better prognosis, and frequently achieve long-term survival. EGFR-tyrosine kinase inhibitor (TKI) is the drug of choice for this cancer; but the disease inevitably progresses, after durable response. The tumor is a mixture of EGFR-TKI sensitive clones and resistant clones, regardless of their molecular mechanisms. EGFR-TKI sensitive clones are very susceptible to this drug, but rarely eradicated; so, withdrawal of the drug permits rapid regrowth of drug sensitive clones, possibly causing "disease flare." Re-administration or continuation of EGFR-TKI can effectively suppress the expansion of drug sensitive clones, even when the total tumor volume continuously increases. Chemotherapy can definitely prolong the survival of patients experiencing EGFR-TKI failure. Prospective clinical trials are warranted to compare efficacies of chemotherapeutic agents. A few retrospective studies suggested that a taxanebased regimen may be superior to others. Here, we reviewed therapeutic options and clinical evidence about this unique disease entity.

Background: Apoptosis plays a role in the development of pleural effusion. Caspase-cleaved cytokeratin 18, a marker for epithelial cell apoptosis, was evaluated in pleural effusion. Methods: A total of 79 patients with pleural effusion were enrolled. The underlying causes were lung cancer (n=24), parapneumonic effusion (n=15), tuberculous effusion (n=28), and transudates (n=12). The levels of M30, an epitope of caspase-cleaved cytokeratin 18, were measured in blood and pleural fluids using enzyme-linked immunosorbent assay along with routine cellular and biochemical parameters. The expression of M30 was evaluated in the pleural tissues using immunohistochemistry for M30. Results: The M30 levels in pleural fluid were significantly higher in patients with tuberculosis ($2,632.1{\pm}1,467.3U/mL$) than in patients with lung cancer ($956.5{\pm}618.5U/mL$), parapneumonic effusion ($689.9{\pm}413.6U/mL$), and transudates ($273.6{\pm}144.5U/mL$; all p<0.01). The serum levels were not significantly different among the disease groups. Based on receiver operating characteristics analysis, the area under the curve of M30 for differentiating tuberculous pleural effusion from all other effusions was 0.93. In the immunohistochemical analysis of M30, all pathologic types of cancer cells showed moderate to high expression, and the epithelioid cells in granulomas showed high expression in tuberculous pleural tissues. Conclusion: Caspase-cleaved cytokeratin 18 was most prominently observed in tuberculous pleural effusion and showed utility as a clinical marker. The main source of M30 was found to be the epithelioid cells of granulomas in tuberculous pleural tissues.

Background: Interferon-${\gamma}$ assays based on tuberculosis (TB)-specific antigens have been utilized for diagnosing and ruling out latent TB and active TB, but their utility is still limited for TB incidence countries. The aim of this study is to understand the clinical utility of enzyme-linked immunospot (ELISpot) assays among patients with clinically suspected TB and healthy adults in clinical practices and community-based settings. Methods: The ELISpot assays (T SPOT.TB, Oxford Immunotec, UK) were prospectively performed in 202 patients. After excluding those with indeterminate results, 196 were included for analysis: 41 were TB patients, 93 were non-TB patients, and 62 were healthy adults. Results: The sensitivity and negative predictive values of the T SPOT.TB assays for the diagnosis of TB were 87.8% and 89.1%, respectively, among patients with suspected TB. The agreement between the tuberculin skin test (10-mm cutoff) and the T SPOT.TB assay was 66.1% (kappa=0.335) in all participants and 80.0% (kappa=0.412) in TB patients. Among those without TB (n=155), a past history of TB and fibrotic TB scar on chest X-rays were significant factors that yielded positive T SPOT.TB results. There was a significant difference in the magnitude of T SPOT.TB spot counts between TB patients and non-TB patients or healthy adults. Conclusion: The T SPOT.TB assay appeared to be a useful test for the diagnostic exclusion of TB. A positive result, however, should be cautiously interpreted for potential positives among those without active TB in intermediate TB incidence areas.

We report the first Korean case of lung diseases caused by Mycobacterium abscessus subsp. bolletii in a previously healthy male, except for a previous history of pulmonary tuberculosis and bronchiectasis. All serial isolates are identified as M. abscessus subsp. bolletii by multi-locus sequence analysis based on the hsp65, rpoB, and 16S rRNA fragments. At the genetic level, the isolate has the erm(41) gene with a T28 sequevar, associated with clarithromycin resistance, and no rrl mutation. The isolate is resistant to clarithromycin. Although the symptoms and radiographic findings have improved after combination of antibiotics, the follow-up sputum cultures are persistently positive.

Glomus tumors of the lung are rare benign neoplasm, originating from modified smooth muscle cells. The patients are usually presented with no or non-specific symptoms such as cough, dyspnea or hemoptysis. Although surgical treatment is considered as the treatment of choice, the endobronchial therapy can be applied to the patients who are unfit for surgical excision. Herein, we describe two rare cases of glomus tumor originated at large airway (trachea and main bronchus) without respiratory symptoms and review their characteristic radiologic, macroscopic and pathological features.

Immunoglobulin G4 (IgG4)-related disease is a newly recognized condition characterized by fibroinflammatory lesions with dense lymphoplasmacytic infiltration, storiform-type fibrosis and obliterative phlebitis. The pathogenesis is not fully understood but multiple immune-mediated mechanisms are believed to contribute. This rare disease can involve various organs and pleural involvement is even rarer. We report a case of IgG4-related disease involving pleura. A 66-year-old man presented with cough and sputum production for a week. Chest radiography revealed consolidation and a pleural mass at right hemithorax. Treatment with antibiotics resolved the consolidation and respiratory symptoms disappeared, but the pleural mass was unchanged. Video-assisted thoracoscopic surgery was performed. Histopathology revealed dense lymphoplasmacytic infiltration and storiform fibrosis with numerous IgG4-bearing plasma cells. The serum IgG4 level was also elevated. Further examination ruled out the involvement of any other organ. The patient was discharged without further treatment and there is no evidence of recurrence to date.

An immunoglobulin G4 (IgG4)-related disease is a recently emerging entity, and a few cases of IgG4-related disease in lung and pleura have been reported. Herein, we report the case of a 74-year-old man with IgG4-related disease of lung and pleura, clinically suspicious of malignant mesothelioma. Chest computed tomography showed diffuse nodular pleural thickening, and microscopic finding disclosed diffuse thickening of visceral pleura with infiltrations of many lymphoplasma cells with increased number of IgG4-positive plasma cells and a few multinucleated giant cells. It is important for pathologists and clinicians to recognize this rare entity and its histologic finding, because it can be confused with malignant tumors on the radiologic examination although it can be treated with steroid therapy.