A review on the potential risks and mechanisms of heavy metal exposure to Chronic Obstructive Pulmonary Disease.

Chronic Obstructive Pulmonary Disease (COPD) is a chronic disease that affects patients as well as the health and economic stability of society as a whole. At the same time, heavy metal pollution is widely recognized as having a possible impact on the environment and human health. Therefore, these diseases have become important global public health issues. In recent years, researchers have shown great interest in the potential association between heavy metal exposure and the development of COPD, and there has been a substantial increase in the number of related studies. However, we still face the challenge of developing a comprehensive and integrated understanding of this complex association. Therefore, this review aimed to evaluate the existing epidemiological studies to clarify the association between heavy metal exposure and COPD. In addition, we will discuss the biological mechanisms between the two to better understand the multiple molecular pathways and possible mechanisms of action involved, and provide additional insights for the subsequent identification of potential strategies to prevent and control the effects of heavy metal exposure on the development of COPD in individuals and populations.

MiR-218 Inhibits CSE-Induced Apoptosis and Inflammation in BEAS-2B by Targeting BRD4.

Background: Chronic obstructive pulmonary disease (COPD) is an age-related disease, and its incidence rate is increasing every year. MicroRNAs (miRNAs) play critical roles in the COPD process and function as key biomarkers or potential therapeutic targets for patients with COPD. However, the potential roles and functional effects of miR-218 in COPD remain undefined. Methods: The expression levels of miR-218 and bromodomain protein 4 (BRD4) were assessed by real-time quantitative polymerase chain reaction (RT-qPCR) or Western blot, respectively. In addition, a COPD cell model was established using cigarette smoke extract (CSE) in bronchial epithelial cell line (BEAS-2B). Enzyme-linked immunosorbent assay (ELISA) kit was applied to measure the concentrations of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8) in cell supernatants of BEAS-2B cells. Moreover, cell apoptosis was examined by flow cytometry assay. The association relationship between miR-218 and BRD4 was confirmed by dual-luciferase reporter and RNA immunoprecipitation assay. Results: MiR-218 was downregulated in COPD and CSE-induced BEAS-2B cells, and it was positively correlated with forced expiratory volume in 1 second (FEV1) % in COPD patients. Mechanically, overexpression of miR-218 or knockdown of BRD4 mitigated apoptosis and inflammation in BEAS-2B cells induced by CSE. Additionally, overexpression of BRD4 weakened the miR-218-mediated effects on CSE-induced BEAS-2B cells. Conclusion: Overexpression of miR-218 inhibited CSE-induced apoptosis and inflammation in BEAS-2B cells by targeting BRD4 expression.

Atypical histiocytosis in the lung.

OBJECTIVE: To report a rare case of atypical histiocytic tumor of the lung with a review of literature. METHODS: The clinical materials were noted. Literature related to this condition from the past 50 years was reviewed from the group of histiocytic tumors. RESULTS AND CONCLUSIONS: Clinical manifestations were non-specific. The imaging characteristics of our case were infiltrative lesions with multiple cysts in both lungs. Pathology showed nodular proliferation of atypical cells. Immunohistochemistry suggested a histiocytic origin of the infiltrating atypical cells. Because the pathological findings did not fall into any particular category of typical histiocytic tumors, the final diagnosis was atypical histiocytic tumor. The presentation of atypical histiocytic tumor of the lungs, only, with infiltrative lesions and multiple air cysts seems very rare, with pathological examination being "gold standard" for the diagnosis.

Creation of lung-targeted dexamethasone immunoliposome and its therapeutic effect on bleomycin-induced lung injury in rats.

OBJECTIVE: Acute lung injury (ALI), is a major cause of morbidity and mortality, which is routinely treated with the administration of systemic glucocorticoids. The current study investigated the distribution and therapeutic effect of a dexamethasone(DXM)-loaded immunoliposome (NLP) functionalized with pulmonary surfactant protein A (SP-A) antibody (SPA-DXM-NLP) in an animal model. METHODS: DXM-NLP was prepared using film dispersion combined with extrusion techniques. SP-A antibody was used as the lung targeting agent. Tissue distribution of SPA-DXM-NLP was investigated in liver, spleen, kidney and lung tissue. The efficacy of SPA-DXM-NLP against lung injury was assessed in a rat model of bleomycin-induced acute lung injury. RESULTS: The SPA-DXM-NLP complex was successfully synthesized and the particles were stable at 4°C. Pulmonary dexamethasone levels were 40 times higher with SPA-DXM-NLP than conventional dexamethasone injection. Administration of SPA-DXM-NLP significantly attenuated lung injury and inflammation, decreased incidence of infection, and increased survival in animal models. CONCLUSIONS: The administration of SPA-DXM-NLP to animal models resulted in increased levels of DXM in the lungs, indicating active targeting. The efficacy against ALI of the immunoliposomes was shown to be superior to conventional dexamethasone administration. These results demonstrate the potential of actively targeted glucocorticoid therapy in the treatment of lung disease in clinical practice.

Primary intravascular large B-cell lymphoma of lung: a report of one case and review.

OBJECTIVE: To investigate the clinicopathological features of primary intravascular large B-cell lymphoma of lung. METHODS: A case of primary pulmonary intravascular large B-cell lymphoma was analysed in histopathology and immunophenotype. RESULTS: The patient is a 42-year-old female who had cough for one year. Computed tomography showed ground-glass opacities and small nodules in bilateral lung fields. Histopathology demonstrated accumulation of similar sized neoplastic cells within alveolar capillaries, widening the alveolar septae. The alveolar structure sustained in part of districtions. Immunohistologically, the tumor cells were positive for CD20 and negative for CD3,CK, which were similar to the diffuse large B-cell lymphoma. CONCLUSIONS: Intravascular large B-cell lymphoma is an uncommon type of non-Hodgkin's lymphoma. Primary pulmonary presentation is even more rare. The diagnosis is based on the histopathology and immunohistochemistry. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2076991810705433.

Clinical analysis of 76 patients pathologically diagnosed with pulmonary cryptococcosis.

The aim of the present study was to investigate the clinical characteristics of pulmonary cryptococcosis patients in China, with analysis of immunocompetent and immunocompromised subjects. We performed a retrospective review of 76 patients diagnosed with tissue-confirmed pulmonary cryptococcosis at the Shanghai Pulmonary Hospital (Shanghai, China) during a 10-yr period (2001-2010). Of 76 patients (54 males and 22 females), 41 (53.95%) were immunocompetent and 35 out of the 41 were asymptomatic. Approximately 80% of the patients had histories suspicious of environmental fungal exposure. Radiological (computed tomography) findings showed predominantly peripheral findings (85.53%, 65 out of 76 patients) including nodular masses (55.26%, 42 out of 76), pneumonic infiltrates (23.68%, 18 out of 76) and mixed type (21.05%, 16 out of 76). 43.42% (33 out of 76) were initially misdiagnosed, often as cancer by false-positive (18)F-fluorodeoxyglucose positron emission tomography ((18)FDG-PET) (28 out of 46 cases). 51 patients received antifungal therapy, 25 patients were clinically observed without treatment. As of December 31, 2010, 71 cases showed total recovery and four cases showed improvement (efficacy rate of 98.68%, 75 out of 76). One HIV-positive case died of cryptococcal meningitis. Incidence of pulmonary cryptococcosis in China may be related to environmental fungal exposures. Most presented as asymptomatic peripheral lung lesions. False-positive (18)FDG-PET examinations often lead to initial clinical misdiagnosis of cancer. Unlike immunocompromised or clinically symptomatic patients, all immunocompetent patients had a good response, either to fluconazole monotherapy or observation, with a tendency for spontaneous remissions in the asymptomatic immunocompetent subjects.

Radical mediastinal nodal removal improves disease-free survival for pulmonary low-grade malignant tumors.

PURPOSE: To investigate the prognostic role of radical lymph node dissection in treatment for pulmonary Low Grade Malignant Tumors (LGMTs); specifically, on the extent of nodal removal and its impact on long-term survival. METHODS: A total of 93 LGMTs cases underwent surgical resection and were histopathologically confirmed. Overall survival rates and disease-free survival were respectively calculated according to the extent of lymph node resection and histopathological grades of tumors. Risk factors of nodal involvement and survival predictors were calculated via multivariate analysis. Life table, Kaplan-Meier, and Cox regression models were used for the statistical analysis. RESULTS: Thirty-eight cases of carcinoid, 17 adenoid cystic carcinomas, and 38 mucoepidermoid carcinomas were included in the current study. Twenty-one cases were high-grade and 72 were low-grade. A total of 813 lymph nodes were removed, at an average of 8.7±5.4 nodes per patient. The numbers of harvested nodes were 11.8±4.5, in the study group via radical nodal removal and 4.0±2.4 nodes per patient in the nodal sampling group. Eleven cases showed lymph nodal involvement (5 mediastinal and 6 hilar lymph node metastasis). No significant differences of overall survival was found among the different histological types (p=0.939), or the extent of nodal removal (p=0.971). Meanwhile, there was a significant difference of disease-free survival (DFS) rates according to the extent of nodal removal (5-YS: 97% of radical nodal dissection vs. 78% of nodal sampling, p=0.038). Overall survival and disease-free survival were closely associated with histological grading (OS: 78% of high grade vs. 97% of low grade, p=0.001; DFS: 57% of high grade vs. 97% of low grade, p<0.0001). CONCLUSIONS: Radical lymph node dissection improved disease-free survival for pulmonary low-grade malignant tumors, although no obvious improvement on overall survival was noticed. Histological grade was the most important prognostic factor in LGMTs.

Fungal granuloma of mediastinal lymph nodes in an immunocompetent host.

This is a case report of mediastinal fungal granuloma in an immunocompetent host. The definite diagnosis was made by pathological biopsy via video-assisted thoracoscopy and silver methenamine staining showed aspergillus hyphae and spores in the epithelioid granuloma. In conclusion, opportunistic pathogenic fungi can cause granulomatous inflammation in mediastinal lymph nodes in an immunocompetent host, as it can do in an immunocompromised host. More attention should be paid on tissue biopsy and pathological examination to ensure a correct diagnosis for these kinds of cases.

Mobilization of bone marrow cells by CSF3 protects mice from bleomycin-induced lung injury.

BACKGROUND: Bone marrow-derived cells may play a role in tissue injury and repair. Growth factors facilitate the mobilization of bone marrow-derived cells to the site of injury. OBJECTIVES: The aim of this study was to determine the effect of the mobilization of autologous bone marrow-derived cells by granulocyte colony-stimulating factor (CSF3) on bleomycin-induced lung injury in mice. METHODS: The bone marrow from male green fluorescent protein transgenic (C57Bl/6J) mice was transplanted into irradiated female C57Bl/6J mice. Bleomycin lung injury was induced in these bone marrow-reconstituted mice and unreconstituted C57Bl/6J mice, and some mice were treated with recombinant CSF3. Lung histology, survival, cytokine expression and matrix metalloproteinase (MMP) expression were evaluated to determine the effect of CSF3 after bleomycin-induced lung injury. RESULTS: Histology and flow cytometry analysis showed successful mobilization of bone marrow-derived cells by CSF3 treatment in the recipient lungs. Importantly, CSF3 attenuated bleomycin-induced lung injury and improved survival. Furthermore, CSF3 administration regulated transforming growth factor-ß, interferon-γ, MMP9 and tissue inhibitors of MMP1 expression during bleomycin injury. CONCLUSIONS: These data demonstrated that the mobilization of bone marrow-derived cells by CSF3 has a protective effect against bleomycin-induced lung injury and fibrosis.

[The effect of autologous bone marrow-derived cells mobilized by granulocyte colony stimulating factor on bleomycin-induced lung injury in mice.].

OBJECTIVE: To investigate the contribution of mobilized autologous bone marrow-derived cells (BMDC) to lung repair after lung injury induced by bleomycin, and the mechanisms of any protective effects conferred by BMDC. METHODS: Sixty marrow-reconstructed mice were randomly divided into 2 groups: group A [bleomycin + granulocyte colony stimulating factor (G-CSF)] and group B (bleomycin + saline). Seventy-five normal mice were randomly divided into 3 groups: group C (bleomycin + G-CSF); group D (bleomycin + saline) and group N (saline only). Each group was further divided into 3 subgroups, which were sacrificed respectively on days 3, 7 and 14. Therapeutic evaluations were made by means of HE stain, Masson's trichrome stain, hydroxyproline concentration and pulmonary permeability index. The expressions of TGF-beta(1), IFN-gamma, MMP-9 and TIMP-1 in the lung tissue were detected by immunohistochemistry. Intrapulmonary BMDC was evaluated by flow cytometry and laser scanning confocal microscope. Another 20 mice were randomly divided into 2 groups including group E (bleomycin + G-CSF) and group F (bleomycin + saline). The survival time of each mouse was observed without end point. RESULTS: The alveolitis score (mean rank 15.3), the pulmonary fibrosis score (46 +/- 8), the hydroxyproline concentrations (0.44 +/- 0.09) microg/mg, the TGF-beta(1) level (111 +/- 23), the IFN-gamma level (250 +/- 72) and the MMP-9 level (59 +/- 19) were significantly decreased in reconstructed treatment group on day 7 as compared to reconstructed control group, which was respectively (mean rank 28.0), (73 +/- 10), (0.52 +/- 0.07) microg/mg, (161 +/- 35), (299 +/- 31) and (314 +/- 77). Likewise, the alveolitis (mean rank 22.7), the pulmonary fibrosis (27 +/- 15), the hydroxyproline concentrations (0.41 +/- 0.05) microg/mg, the pulmonary permeability index (43.8 +/- 9.9) x 10(-3), the TGF-beta(1) level (132 +/- 55), the IFN-gamma level (178 +/- 23), and the MMP-9 level (101 +/- 54) in non-reconstructed treatment group on day 7 were significantly lower than those in non-reconstructed control group, (mean rank 33.9), (56 +/- 13), (0.49 +/- 0.08) microg/mg, (54 +/- 9) x 10(-3), (320 +/- 98), (409 +/- 61), (288 +/- 75), the differences being statistically significant (P < 0.05). The intrapulmonary BMDC level of reconstructed treatment group (0.65 +/- 0.13) was significantly higher than that in reconstructed control group (0.46 +/- 0.11), P < 0.05. CONCLUSION: Mobilization of BMDC by G-CSF showed a protective effect on lung injury induced by bleomycin in mice, but did not have significant influence on survival time.

[Idiopathic lymphoid interstitial pneumonia: a report of 3 cases and literature review].

OBJECTIVE: To analyze the clinical, radiological and pathological characteristics of idiopathic lymphoid interstitial pneumonia (idiopathic LIP) and to discuss its diagnosis, treatment and prognosis. METHODS: Respiratory physicians, pathologists and radiologists together retrospectively analyzed the clinical, chest roentgenogram, computerized tomography, pathological, diagnostic and therapeutic data of 3 patients with idiopathic LIP confirmed by lung biopsy, and reviewed the relevant literatures. RESULTS: The major symptoms of the 3 cases of idiopathic LIP were progressive dyspnea and dry cough. Higher levels of gamma-globulins in serum were found in all the cases. The characteristic radiographic manifestations were bilateral diffuse nodules and cysts. The pathologic feature was diffuse interstitial inflammation with polyclonal lymphocytes infiltration, especially with plasma lymphocytes. Corticosteroids and cytotoxic agents were used and good response to therapy was observed in the cases. CONCLUSIONS: Idiopathic LIP has some characteristics on the clinical, radiological and pathological features, but the best diagnostic method depends on a clinical-radiological-pathological approach. The disease usually shows good response to combinative therapy of corticosteroids and cytotoxic agents.

[Application of quantitative polymerase chain reaction in the differentiation of sarcoidosis and proliferative tuberculosis].

OBJECTIVE: To evaluate the role of mycobacterial infection in the pathogenesis of sarcoidosis by examination of mycobacterial DNA in tissue samples of sarcoidosis and tuberculosis, and to examine the value of quantitative real-time polymerase chain reaction (PCR) in the differentiation of the two diseases. METHODS: Mycobacterium tuberculosis DNA was measured by quantitative real-time PCR from formalin-fixed and paraffin-embedded sections of biopsy samples of lymph nodes and lung tissues from 31 patients with sarcoidosis, 30 patients with tuberculosis and 15 patients with other diseases (as the control samples) in Shanghai Pulmonary Hospital from January 1998 to December 2003. Lung tissues from 15 normal embryonic mice served as the negative control. RESULTS: The positive rate of mycobacterial DNA in the tuberculosis samples (30/30) was higher than that of the sarcoidosis samples (6/31) and of the control samples (2/15). The difference between sarcoidosis and normal samples showed no statistical significance. The absolute and relative copies of mycobacterial DNA in the tuberculosis samples were significantly higher than those in the sarcoidosis and the control samples; while there was no statistical difference between the sarcoidosis and the control samples. There was no positive result in the lung tissues of the embryonic mice. CONCLUSIONS: The results do not show any relationship between mycobacterial infection and sarcoidosis. Quantitative PCR may be a reliable method for the differentiation of sarcoidosis from tuberculosis.

[Clinical analysis of 25 cases of biopsy-proven cryptogenic organizing pneumonia].

OBJECTIVE: To analyze the clinical, radiological and pathological features, diagnosis and response to therapy as well as prognosis of 25 cases of cryptogenic organizing pneumonia (COP). METHODS: Twenty-five subjects with COP confirmed by lung biopsy in Shanghai Pulmonary Hospital from January of 2000 to April of 2006 were retrospectively reviewed. Secondary reaction to infections, drugs, radiation, connective tissue diseases and various noxious agents were excluded. Their clinical-pathological characteristics, radiological features, response to treatment, relapse, survival were obtained from medical records and a follow-up patient questionnaire. RESULTS: There were 6 males and 19 females, with a mean age of 56 years (range 40 - 73 years). The presentations included cough (25/25), clear sputum (21/25), dyspnea (17/25), hemoptysis (5/25), fever and sweats (3/25), and "Velcro" crackles (18/25). Four of them were smokers, 11 had allergic reaction to some drugs, and 11 had some industrious dust inhalation. In 23 cases the specimens were obtained by video-assisted thoracoscopy and 2 cases by transbronchial lung biopsy. Bilateral lung involvement was present in 23 cases and all of them had at least two different radiological manifestations. Twenty-four cases showed a sub-pleural distribution. Bilateral patchy alveolar and ground glass involvement were found in 8 cases, airspace consolidation in 8 cases, mass in 11 cases, irregular lines in 10 cases, small nodules (<10 mm) in 4 cases. Two patients received operation. Corticosteroid therapy was administered to 23 patients. Seventeen cases were cured, but 8 of them relapsed after stopping (n = 2) and tapering (n = 6, when prednisone less than 5 - 10 mg/d) of corticosteroids within one to two years of therapy. CONCLUSIONS: COP is not very rare in China. The clinical-radiological-pathological diagnosis (CRP) is the most important diagnostic method. Corticosteroid is the first choice for COP therapy. The prognosis of COP is good if therapy is started in time, but relapse is common.

[Result of surgical treatment and prognostic factors in giant mass lung cancer].

OBJECTIVE: To investigate the role of surgery in the treatment of giant mass lung cancer and to analyze prognostic factors affecting surgical result. METHODS: From August 1992 to August 2005, the clinical data of 137 patients with giant mass lung cancer ( > or =8 cm in diameter) were retrospectively reviewed. 122 cases had radical resection with 63 lobectomies, 48 pneumonectomy and 11 other resection modes, the remaining 15 patients underwent palliative resection. The prognostic factors including sex, tumor size, p-TNM stage, T stage, N stage, histological types and operation extent were analyzed with SPSS 13.0 software. The survival rate was calculated by Kaplan-Meier method and logrank was used for comparing survival difference. Univariate and multivariate prognostic factors for survival were analyzed by Cox proportional hazard regression model. RESULTS: The overall 1-, 3- and 5-year survival rate was 76.0%, 49.2% and 40.1%, respectively. Sex (P = 0.001), p-TNM stage (P = 0.001), N stage (P = 0.042), surgical approach (P = 0.026) and T stage (P = 0.006) were found to be prognostic factors in Cox univariate analysis. p-TNM stage (P = 0.001) were identified as an independent prognostic factor in Cox multivariate analysis. CONCLUSION: p-TNM stage is the crucial prognostic factor in surgical treatment for giant mass lung cancer. Strict selection of candidate for resection and complete resection may be helpful in improving survival in patient with giant mass lung cancer.

[Study of prognostic factors in patients with stage I non-small cell lung cancer].

OBJECTIVE: To analyze the prognostic factors in patients with stage I non-small cell lung cancer (NSCLC). METHODS: Fifty-eight patients with stage I NSCLC treated from 1991 to 1995 were retrospectively reviewed. The clinical features, histopathology and prognostic factors were analyzed by SPSS10.0 statistic software. The expression of c-myc, MDM2, c-erbB-2, EGFR, p53, p14(ARF), p16(INK4), p21(WAF1) and nm23 was detected by immunohistochemical assay. The overall survival rate, local-regional control rate and distant metastasis rate were observed. RESULTS: The overall survival rate, local-regional recurrent rate and distant metastasis rate were 71.1%, 11.1% and 33.5%, respectively. In univariate analysis, tumor cell differentiation was an independent prognostic factor (P = 0.028); overexpression of c-myc or c-erbB-2 had significantly poor overall survival and high distant metastasis rate (P < 0.05). The total oncogene immunoreactive score (IRS) and comprehensive IRS were associated with poor overall survival. In multivariate analysis, tumor cell differentiation and comprehensive IRS were independent prognostic factors for overall survival. Among the high-risk group of patients, those who had received chemotherapy seemed to have a higher overall survival rate and a lower distant metastasis rate in this study, but the difference was not statistically significant. CONCLUSION: For stage I NSCLC patients, tumor cell differentiation and comprehensive IRS are independent prognostic factors for overall survival. Adjuvant chemotherapy might somehow improve the survival for the patients with high-risk factors.

[A clinicopathologic study on neoadjuvant chemotherapy in the treatment of non-small-cell lung cancer].

BACKGROUND: To explore the clinicopathological changes of non-small cell lung cancer tissues after neoadjuvant chemotherapy with MVP (MMC+VDS+DDP) regimen and its concordance with clinical evaluation, and to study the clinical value of neoadjuvant chemotherapy. METHODS: A total of 84 patients with NSCLC were randomized into combinated therapy group (42 cases) and surgical group (42 cases). The combinated therapy group were given MVP regimen for 2 cycles before operation and 2-4 cycles after operation, however, the surgical group only received surgical treatment. The efficacy of preoperative chemotherapy were determined by pathologic examination under light microscope and electron microscope and clinical evaluation. RESULTS: Combinated therapy group showed various degrees of degeneration and necrosis of tumor cells, which was not found in surgical group. The overall response rate of neoadjuvant chemotherapy was 59.5% (25/42) by both pathological and clinical evaluation. The coincidence ratio of the two evaluation methods was 71.4% (Kappa value=0.407,P < 0.01). Between the two groups, there was a significant difference in total survival rate (P=0.047). And further analysis showed that survival rate was remarkably different in patients with stage III between the two groups (P=0.037), but not in those with stage I and II (P > 0.05). CONCLUSIONS: Degeneration and necrosis with fibrosis are the main pathological phenotypes of the primary lesion after induction chemotherapy, which can be showed by clinical evaluation to chemotherapy efficacy. The preoperative and postoperative adjuvant chemotherapy may be benefical to patients with stage-III NSCLC.

[Biologic significance of thyroid transcription factor-1 and surfactant protein expression in pulmonary sclerosing hemangioma].

OBJECTIVE: To investigate the biologic significance of thyroid transcription factor-1 (TTF-1) and surfactant protein A (SP-A) and SP-B expression in pulmonary sclerosing hemangioma (PSH). METHODS: TTF-1, SP-A, SP-B, epithelial membrane antigen (EMA), pancytokeratin (AE(1)/AE(3)), vimentin, CK7, CK5/6, calretinin, S-100, neuron specific enolase (NSE), synaptophysin (Syn), chromogranin A (CgA), CD(34), Factor VIII and smooth muscle actin (SMA) in 42 patients with PSH were examined with immunohistochemistry, while samples from 10 patients were also observed by electron microscope. RESULTS: Histopathologically, PSH mainly consisted of both surface lining cuboidal cells and pale polygonal cells. Both of them were stained with TTF-1, EMA and vimentin, whereas SP-A, SP-B, pancytokeratin and CK7 were only positive in surface lining cuboidal cells. Syn, NSE, S-100 and CgA showed scattered positivity in these cells. There was no significant difference in the expressions of TTF-1 and EMA between these two cell types (P > 0.05), whereas the difference was significant in the expression of vimentin (P < 0.01). The ultrastructural features cannot differentiate these two cells by electron microscope. CONCLUSIONS: It is suggested that PSH is derived from primitive respiratory epithelium, and both surface lining cuboidal cells and pale polygonal cells were entity cells of the tumor. Examination of different immunohistochemical markers including TTF-1, SP-A, SP-B, pancytokeratin, EMA and vimentin is helpful in the diagnosis and differential diagnosis of PSH.