Series "matrix metalloproteinases in lung health and disease": Matrix metalloproteinases in COPD.

There is considerable evidence that matrix metalloproteinases (MMPs) are up- and/or downregulated in chronic obstructive pulmonary disease (COPD), particularly in emphysema, in which they probably participate in proteolytic attack on the alveolar wall matrix. Recent data suggest that MMPs also have major roles in driving inflammation or shutting it down, as well as modifying the release of fibrogenic growth factors, processes that are important in the genesis of the various lesions of COPD. In cigarette smoke-induced animal models of emphysema, MMP-12 appears to play a consistent and important role, whereas the data for other MMPs are difficult to interpret. In human lungs, evidence for a role for MMPs is more tenuous and there are numerous contradictions in the literature. Little is known about the effects of MMPs in small airway remodelling, smoke-induced pulmonary hypertension and chronic bronchitis, but MMP-12 participates in experimental small airway modelling. To date, the accumulated data suggest that selective inhibition of MMP-12 might be a viable therapy for emphysema and small airway remodelling, but subtle differences in the functions of MMP-12 in animals and humans mandate caution with this approach. Whether inhibition of other MMPs might be useful is unclear.

Pulmonary hypertension and vascular oxidative damage in cigarette smoke exposed eNOS(-/-) mice and human smokers.

CONTEXT: Cigarette smoke is known to be associated with pulmonary hypertension in humans and in animal models. Although the etiology of pulmonary hypertension in smokers is not understood, recent work has suggested a role for inducible nitric oxide synthase (iNOS) in inducing oxidative stress. OBJECTIVE AND METHODS: To further evaluate this question, we assessed eNOS-/- mice exposed to air or cigarette smoke for the presence of pulmonary hypertension and examined vascular remodeling and expression of nitrotyrosine, a marker of reactive nitrogen species-induced oxidative damage, using immunohistochemistry. To ascertain whether oxidants may play a role in humans, we also examined lung tissue from nonsmokers, and patients with chronic obstructive pulmonary disease (COPD) with and without pulmonary hypertension. RESULTS: We found that eNOS(-/-) mice developed increased pulmonary arterial pressure after six months cigarette smoke exposure, and this was associated with vascular remodeling and increased vascular nitrotyrosine staining. iNOS gene expression was decreased in the pulmonary arteries of the smoke exposed animals, and no protein was detectable by immunohistochemistry. In humans, vascular nitrotyrosine staining intensity was increased in smokers with COPD compared to nonsmokers, and further increased in smokers with combined COPD and pulmonary hypertension. CONCLUSIONS: We conclude that cigarette smoke-induced pulmonary hypertension is associated with evidence of oxidative vascular damage by reactive nitrogen species, but that iNOS does not appear to be the major contributor to such damage. Most likely the source of reactive nitrogen species is the cigarette smoke itself.

AZD9668: pharmacological characterization of a novel oral inhibitor of neutrophil elastase.

N-{[5-(methanesulfonyl)pyridin-2-yl]methyl}-6-methyl-5-(1-methyl-1H-pyrazol-5-yl)-2-oxo-1-[3-(trifluoromethyl)phenyl]-1,2-dihydropyridine-3-carboxamide (AZD9668) is a novel, oral inhibitor of neutrophil elastase (NE), an enzyme implicated in the signs, symptoms, and disease progression in NE-driven respiratory diseases such as bronchiectasis and chronic obstructive pulmonary disease via its role in the inflammatory process, mucus overproduction, and lung tissue damage. In vitro and in vivo experiments were done to evaluate the binding kinetics, potency, and selectivity of AZD9668, its effects in whole-blood and cell-based assays, and its efficacy in models of lung inflammation and damage. In contrast to earlier NE inhibitors, the interaction between AZD9668 and NE was rapidly reversible. AZD9668 was also highly selective for NE over other neutrophil-derived serine proteases. In cell-based assays, AZD9668 inhibited plasma NE activity in zymosan-stimulated whole blood. In isolated human polymorphonuclear cells, AZD9668 inhibited NE activity on the surface of stimulated cells and in the supernatant of primed, stimulated cells. AZD9668 showed good crossover potency to NE from other species. Oral administration of AZD9668 to mice or rats prevented human NE-induced lung injury, measured by lung hemorrhage, and an increase in matrix protein degradation products in bronchoalveolar lavage (BAL) fluid. In an acute smoke model, AZD9668 reduced the inflammatory response to cigarette smoke as indicated by a reduction in BAL neutrophils and interleukin-1ß. Finally, AZD9668 prevented airspace enlargement and small airway wall remodeling in guinea pigs in response to chronic tobacco smoke exposure whether dosed therapeutically or prophylactically. In summary, AZD9668 has the potential to reduce lung inflammation and the associated structural and functional changes in human diseases.

Induction of endometrial peroxidase synthesis and secretion by estrogen and estrogen antagonist.

Synthesis of peroxidase was induced in the uterine epithelium of immature rats by multiple doses over a 24-96-h period of either 17 beta-estradiol, the estrogen-antagonist Parke-Davis CI-628, or a combination of estradiol plus antagonist. Endogenous peroxidase activity first appeared in the cisternae of the rough endoplasmic reticulum of surface epithelial and glandular cells within 24-48 after the initial injection. Uterine peroxidase activity was also visible in the cisternae of the Golgi apparatus, in Golgi-derived secretory granules, and within the uterine and glandular lumen. Some cells of the epithelium produced little or no peroxidase, even after 96 h. Whereas the antagonist appeared to induce synthesis and secretion of peroxidase, neither the antagonist alone nor the combined treatment (estradiol plus antagonist) reproduced the estradiol-mediated growth in organ size and increased lumen diameter.

Short-term exposure to cigarette smoke induces endothelial dysfunction in small intrapulmonary arteries: analysis using guinea pig precision cut lung slices.

The pathogenesis of cigarette smoke-induced pulmonary hypertension is not understood. We have previously shown that smoke rapidly and persistently, but discoordinately, upregulates gene expression of mediators that control vasoconstriction, vasoproliferation, and vasorelaxation in small intrapulmonary arteries. To investigate the possibility that smoke also induces endothelial dysfunction, a finding common to other forms of pulmonary hypertension, we exposed guinea pigs to smoke or air (control) daily for 2 wk and then prepared precision-cut lung slices. After exposure to endothelin-1, a vasoconstrictor, intra-acinar arteries in lung slices derived from smoke-exposed animals constricted more rapidly (greater constriction at a given concentration of endothelin) than did vessels from air-exposed animals. To examine relaxation responses, arteries were constricted with the vasoconstrictor U-46619 and then relaxed with progressively increasing doses of acetylcholine. Vessels from smokers had a delayed response to acetylcholine compared with vessels from controls. The NO synthase inhibitor N(G)-nitro-L-arginine methyl ester reduced relaxation in both control and smoke-exposed arteries, whereas the NO donor sodium nitroprusside increased relaxation of the smoke-exposed arteries, confirming that endothelial dysfunction with decreased effective NO production is present. These findings show that precision cut lung slices can be used to examine the physiological effects of cigarette smoke on intra-acinar pulmonary arteries and indicate that even relatively short-term exposure to smoke produces endothelial dysfunction with a resulting tendency to earlier constriction and later relaxation in cigarette smokers. These changes may be important in the development of pulmonary hypertension.

New Insights on Diagnostic Reproducibility of Biphasic Mesotheliomas: A Multi-Institutional Evaluation by the International Mesothelioma Panel From the MESOPATH Reference Center.

INTRODUCTION: The 2015 WHO classification of tumors categorized malignant mesothelioma into epithelioid, biphasic (BMM), and sarcomatoid (SMM) for prognostic relevance and treatment decisions. The survival of BMM is suspected to correlate with the amount of the sarcomatoid component. The criteria for a sarcomatoid component and the interobserver variability between pathologists for identifying this component are not well described. In ambiguous cases, a "transitional" (TMM) subtype has been proposed but was not accepted as a specific subtype in the 2015 WHO classification. The aims of this study were to evaluate the interobserver agreement in the diagnosis of BMM, to determine the nature and the significance of TMM subtype, and to relate the percentage of sarcomatoid component with survival. The value of staining for BRCA-1-associated protein (BAP1) and CDKN2A(p16) fluorescence in situ hybridization (FISH) were also assessed with respect to each of the tumoral components. METHODS: The study was conducted by the International Mesothelioma Panel supported by the French National Cancer Institute, the network of rare cancer (EURACAN) and in collaboration with the International Association for the Study of Lung Cancer (IASLC). The patient cases include a random group of 42 surgical biopsy samples diagnosed as BMM with evaluation of SMM component by the French Panel of MESOPATH experts was selected from the total series of 971 BMM cases collected from 1998 to 2016. Fourteen international pathologists with expertise in mesothelioma reviewed digitally scanned slides (hematoxylin and eosin - stained and pan-cytokeratin) without knowledge of prior diagnosis or outcome. Cases with at least 7 of 14 pathologists recognizing TMM features were selected as a TMM group. Demographic, clinical, histopathologic, treatment, and follow-up data were retrieved from the MESOBANK database. BAP1 (clone C-4) loss and CDKN2A(p16) homozygous deletion (HD) were assessed by immunohistochemistry (IHC) and FISH, respectively. Kappa statistics were applied for interobserver agreement and multivariate analysis with Cox regression adjusted for age and gender was performed for survival analysis. RESULTS: The 14 panelists recorded a total of 544 diagnoses. The interobserver correlation was moderate (weighted Kappa = 0.45). Of the cases originally classified as BMM by MESOPATH, the reviewers agreed in 71% of cases (385 of 544 opinions), with cases classified as pure epithelioid in 17% (93 of 544), and pure sarcomatoid in 12% (66 of 544 opinions). Diagnosis of BMM was made on morphology or IHC alone in 23% of the cases and with additional assessment of IHC in 77% (402 of 544). The median overall survival (OS) of the 42 BMM cases was 8 months. The OS for BMM was significantly different from SMM and epithelioid malignant mesothelioma (p < 0.0001). In BMM, a sarcomatoid component of less than 80% correlated with a better survival (p = 0.02). There was a significant difference in survival between BMM with TMM showing a median survival at 6 months compared to 12 months for those without TMM (p < 0.0001). BAP1 loss was observed in 50% (21 of 42) of the total cases and in both components in 26%. We also compared the TMM group to that of more aggressive patterns of epithelioid subtypes of mesothelioma (solid and pleomorphic of our large MESOPATH cohort). The curve of transitional type was persistently close to the OS curve of the sarcomatoid component. The group of sarcomatoid, transitional, and pleomorphic mesothelioma were very close to each other. We then considered the contribution of BAP1 immunostaining and loss of CDKN2A(p16) by FISH. BAP1 loss was observed in 50% (21 of 41) of the total cases and in both component in 27% of the cases (11 of 41). There was no significant difference in BAP1 loss between the TMM and non-TMM groups. HD CDKN2A(p16) was detected in 74% of the total cases with no significant difference between the TMM and non-TMM groups. In multivariate analysis, TMM morphology was an indicator of poor prognosis with a hazard ratio = 3.2; 95% confidence interval: 1.6 - 8.0; and p = 0.003 even when compared to the presence of HD CDKN2A(p16) on sarcomatoid component (hazard ratio = 4.5; 95% confidence interval: 1.2 - 16.3, p = 0.02). CONCLUSIONS: The interobserver concordance among the international mesothelioma and French mesothelioma panel suggests clinical utility for an updated definition of biphasic mesothelioma that allows better stratification of patients into risk groups for treatment decisions, systemic anticancer therapy, or selection for surgery or palliation. We also have shown the usefulness of FISH detection of CDKN2A(p16) HD compared to BAP1 loss on the spindle cell component for the separation in ambiguous cases between benign florid stromal reaction from true sarcomatoid component of biphasic mesothelioma. Taken together our results further validate the concept of transitional pattern as a poor prognostic indicator.

Airway remodeling in the smoke exposed guinea pig model.

Although small airway remodeling (SAR) leading to airflow obstruction is a common consequence of human cigarette smoking, the airways have been largely ignored in animal models of chronic obstructive pulmonary disease (COPD). We examined lung structure in a guinea pig model of chronic cigarette smoke exposure to ascertain whether smoke induced SAR, and to evaluate how these anatomic lesions correlate with physiologic changes. We used tissue from guinea pigs exposed to cigarette smoke or air for 6 mo. Pulmonary function tests were performed, and histologic sections were prepared. Airspace size (Lm) and changes in the structure of the small airways were evaluated by morphometric analysis. Chronic smoke exposure was associated with increased airway wall thickness and increased amounts of thick collagen fibers in the walls of the small airways, as well as with increased Lm. The increase in thick collagen fibers related negatively to peak expiratory volume (PEF) and the ratio of forced expiratory volume in 1 s to forced ventilatory capacity (FEV(0.1)/FVC), and positively to airway resistance. Physiologic lung volumes were predicted by airspace size, but residual volume (RV) and total lung capacity (TLC) also were related to airway wall thickness. Amounts of smooth muscle were not changed and did not predict any physiologic abnormalities. We conclude that cigarette smoke exposure results in SAR in the guinea pig, alterations that are reflected in increased airways resistance with diminished airflow and air trapping, mimicking human disease. This model should prove useful in further investigations into the mechanisms of airway remodeling.

Direct enhancement by cigarette smoke of asbestos fiber penetration and asbestos-induced epithelial proliferation in rat tracheal explants.

Tracheal explants from Sprague-Dawley rats were briefly exposed to cigarette smoke or air (control) and then to amosite asbestos. Asbestos fibers in or under the tracheal epithelium were counted and extent of hyperplastic lesions was ascertained at 24 hours, 72 hours, and 1 week after exposure. Smoke-exposed cultures showed significantly greater numbers of fibers in the epithelium and greater proliferative activity compared to findings in cultures not exposed to smoke. These observations indicate that very short exposure to cigarette smoke can directly affect the response of the epithelium to asbestos fibers and that smoke exposure need not be concurrent with asbestos exposure for such event to occur. These reactions may play a role in the greater incidences of lung cancer and asbestosis seen in asbestos-exposed workers who smoke.

Ambient particulate matter causes activation of the c-jun kinase/stress-activated protein kinase cascade and DNA synthesis in lung epithelial cells.

Numerous epidemiological studies have demonstrated a positive association between ambient air pollution and adverse health effects including respiratory morbidity, asthma, and lung cancer. It has been suggested in some experimental studies that airborne particulate matter (PM) can produce inflammatory effects, but nothing is known about the possible proliferative and carcinogenic effects of these particles on cells of the lung. We show here that exposure of pulmonary epithelial cells, a cell type affected in acute lung injury, asthma, and lung carcinomas, to nontoxic concentrations of PM in vitro results in increases in c-jun kinase activity, levels of phosphorylated cJun immunoreactive protein, and transcriptional activation of activator protein-1-dependent gene expression. These changes are accompanied by elevations in numbers of cells incorporating 5'-bromodeoxyuridine, a marker of unscheduled DNA synthesis and/or cell proliferation. Data here are the first to demonstrate that interaction of ambient PM with target cells of the lung initiates a cell signaling cascade related causally to aberrant cell proliferation and carcinogenesis.

Converting structural changes upon oxidation of cytochrome c to electrostatic reorganization energy.

The observed X-ray structural differences between reduced and oxidized cytochrome c are converted to electrostatic energy. This conversion is used to estimate the protein reorganization energy which determines the protein contribution to the activation barrier for the electron transfer reaction. It is shown that the reorganization energy of cytochrome c is much smaller than the corresponding energy for electron transfer in water and that this is consistent with the role for cytochromes as electron transfer catalysts.

Pulmonary epithelial expression of human alpha1-antitrypsin in transgenic mice results in delivery of alpha1-antitrypsin protein to the interstitium.

Alpha1-antitrypsin (alpha1AT) therapy is used as a treatment for alpha1AT deficiency. It has also been proposed as a therapy for cigarette smoke-induced emphysema, although the efficacy of such therapy is as yet unproven. Moreover, the optimal route of delivery of alpha1AT to the lung interstitium, the crucial locus of action, is unknown. We created transgenic mice with expression of the human alpha1AT gene directed by a human surfactant protein C (SpC) promoter fragment or a rat Clara cell 10-kDa protein (CC10) promoter fragment in order to examine the ability of pulmonary epithelial cell expression of alpha1AT to deliver protein to the interstitium, and to produce a model that would allow studies on the efficacy of alpha1AT in preventing lung damage after cigarette smoke exposure. Four transgenic lines were studied. In situ hybridization and light microscopic immunohistochemistry showed that two CC10 driven lines expressed human alpha1AT in type 11 alveolar cells and airway epithelial cells; alpha1AT expression was seen in the alveolar parenchyma in two SpC driven lines, and in small airway epithelium in one of the SpC lines. Electron microscopic immunochemistry showed the presence of the human alpha1AT protein in the interstitium in all lines. Mean levels of human protein varied from 0.37 to 2.9 microg/g lung protein and serum levels from 0.72 to 1.3 microg/ml, compared to normal human serum alpha1AT levels of 2-5 mg/ml. We conclude that transgene-mediated expression of alpha1AT in pulmonary epithelial cells results in diffuse expression of the transgene in the alveolar parenchyma and reproducibly leads to transfer of protein to the interstitium. The present model is, however, limited by low levels of protein production; limited protein production may be a problem in other forms of gene therapy in which relatively large amounts of extracellular protein are needed in the lung for a therapeutic effect.

Changing trends in US mesothelioma incidence.

The correspondence by Weillet al (below) refers to a letter by Greenberg, which was published in February's edition of the journal. We regret the late appearance of this printed response, which arises from an administrative error. An electronic version of this text was posted on the website on 1 February 2005.

Pleuropulmonary disease during bromocriptine treatment of Parkinson's disease.

Pleuropulmonary disease has been observed in eight patients with Parkinson's disease treated with bromocriptine or its related compound, mesulergine. The pleuropulmonary changes included pleural effusions, pleural thickening, and parenchymal lung disease. The patients developed symptoms from nine months to four years after starting treatment with bromocriptine that varied in dosage from 22 to 50 mg daily, while the patient receiving mesulergine was taking 6 mg daily. No other cause was found for the pleuropulmonary changes. In six patients the medication was discontinued with subsequent clinical, physiologic, and radiologic improvement. In two patients bromocriptine treatment was continued for one to two years, and in one patient there was further physiologic and radiologic progression of the pleuropulmonary changes. These findings suggest a causal relationship between bromocriptine treatment and pleuropulmonary disease. We recommend a chest roentgenogram and pulmonary function evaluation prior to bromocriptine treatment with follow-up studies if the patient develops respiratory symptoms. Physicians prescribing bromocriptine should be aware of this side effect to ensure early recognition and prompt withdrawal of bromocriptine therapy.

Immunohistochemistry of meningiomas including the angioblastic type.

Immunohistochemical techniques were used to determine the intermediate filament content of normal arachnoidal cells, meningiomas (including the so-called hemangiopericytoma of the meninges), soft tissue hemangiopericytoma, and the normal pericyte. Arachnoid granulations and all types of meningioma stained similarly: positive for vimentin and variably positive for keratin. Soft tissue hemangiopericytomas and normal pericytes were negative for both vimentin and keratin. This suggests that the "hemangiopericytoma" of the meninges is a variant of meningioma and not of pericytic origin.

Asbestos and cigarette smoke cause increased DNA strand breaks and necrosis in bronchiolar epithelial cells in vivo.

Coexposures to asbestos and cigarette smoke cause increased risks of lung cancer in asbestos workers. Although these carcinogens cause DNA damage to epithelial cells in vitro via generation of reactive oxygen species (ROS), it is unclear whether they cause injury to bronchiolar epithelial cells (i.e., the target cells of lung cancers in vivo). We exposed rats to amosite asbestos, cigarette smoke, and the two agents in combination for 1, 2, and 14 d. Numbers of cells exhibiting DNA strand breaks in comparison to sham rats were then evaluated in lungs using the terminal deoxynucleotidyl transferase (TDT)-mediated dUTP-biotin nick end labeling (TUNEL) method and by transmission electron microscopy (TEM). Increases in TUNEL-positive, necrotic epithelial cells occurred after exposure to asbestos alone and in an additive fashion after smoke and asbestos in combination. These results indicate that DNA strand breakage and necrosis are prominent mechanisms of injury by asbestos fibers and cigarette smoke in vivo to epithelial cells of the respiratory tract, thus validating in vitro observations from a number of laboratories.

Immunohistochemical staining for vimentin and keratin in malignant mesothelioma.

Because tissue culture studies have suggested that mesothelial cells might produce large amounts of vimentin, I stained eight mesotheliomas (two fixed in alcohol) for vimentin using the Gown and Vogel monoclonal antibody 43 beta E8. The two tumors that had alcohol fixed blocks were strongly positive for vimentin, whereas one of the tumors fixed only in formalin showed moderately strong staining and two others showed very weak focal positivity; the remaining tumors were negative. In the mesotheliomas that did stain, both epithelial and spindled elements gave a positive reaction. Three alcohol-fixed lung cancers and two blocks of alcohol-fixed pleura failed to stain for vimentin. By contrast, all mesotheliomas and carcinomas, whether alcohol or formalin fixed, as well as sections of pleura, were strongly positive when stained with anticytokeratin antibody 35 beta H11. I conclude that the combination of staining for vimentin and keratin might be a useful diagnostic finding in malignant mesothelioma, but that specially fixed material is required for reliable vimentin staining.

Intravascular and sclerosing bronchioloalveolar tumor. A pulmonary sarcoma of probable vascular origin.

A case of intravascular and sclerosing bronchioloalveolar tumor (IVSBAT) studied by light microscopy and electron microscopy is reported. Light microscopy revealed typical nodules composed of plump tumor cells in the peripheral regions and central areas of hyalinization. Histochemical examination revealed that the matrix material contained hyaluronic acid. Around the periphery of the nodules, tumor cells and matrix material were observed within the alveolar walls. Tumor was also present in numerous small bood vessels and lymphatics. Electron microscopy demonstrated that the tumor cells were polygonal or elongated and were connected by small junctions. The cytoplasm was filled with fine filaments, and dense bodies typical of those seen in smooth muscle cells were occasionally observed. Pinocytotic vesicles and basement membranes were also present. Some cells formed vessel-like lumina. Rows of tumor cells were identified within alveolar walls where they at first proliferated without disturbing the overall architecture; increasing numbers of tumor cells and matrix material gradually widened the alveolar walls, and the tumor finally expanded into the alveolar spaces. The ultrastructural features of the tumor cells are consistent with an origin form pericytes or endothelial cells; we suggest that IVSBAT is actually a sarcoma of vasoformative cells which arises within the alveolar walls, perhaps in multicentric fashion. We propose that the tumor be renamed "sclerosing interstitial vascular sarcoma".

Ferruginous bodies and the histologic evaluation of dust exposure.

Ferruginous bodies are frequently observed in histologic sections of lung from individuals with occupational or environmental exposure to asbestos and other mineral dusts. Analysis of large numbers of such ferruginous bodies has demonstrated that the types with asbestos cores can be differentiated by light microscopy from several chemically and morphologically distinct classes of nonasbestos ferruginous bodies, including those formed on sheet silicates (talc and mica), carbon, rutile, and fly ash. Light-microscopic screening of lung tissue sections for ferruginous bodies is a reliable, convenient, and economical method for documenting exposure to a variety of mineral dusts and can assist in determining the etiology of pneumoconiotic lesions. Because tissue sections are relatively insensitive detectors of particles, the finding of ferruginous bodies in section implies heavy dust exposure.

Immunohistochemical staining for keratin and carcinoembryonic antigen in the diagnosis of malignant mesothelioma.

Using formalin-fixed, paraffin-embedded tissue and commercial antisera, we evaluated the usefulness of immunohistochemical staining for carcinoembryonic antigen (CEA) and keratin in the diagnosis of malignant mesothelioma. All 18 adenocarcinomas of lung examined stained for CEA, usually strongly, while only eight of 22 mesotheliomas stained for CEA and the staining was generally weak. Staining for keratin was observed in 10 of 22 mesotheliomas and 12 of 18 adenocarcinomas; there were no differences in intensity of staining between the groups. We conclude that strong diffuse staining for CEA favors a diagnosis of carcinoma, and negative staining for CEA is against a diagnosis of carcinoma, but these are relative and not absolute criteria. We find that staining for keratin is of no use in distinguishing these types of tumors.

Small cell squamous and mixed small cell squamous--small cell anaplastic carcinomas of the lung.

Five patients are presented who had neoplasms which, by light microscopy and in two cases cytologically, appeared to be small cell anaplastic (polygonal and fusiform cell type) carcinomas of the lung. However, by electron microscopy, four of the carcinomas exhibited squamous characteristics including desmosomes and tonofilament bundles, and lacked demonstrable neurosecretory granules, suggesting that they were small cell squamous carcinomas. The fifth carcinoma contained cells with neurosecretory granules as well as cells demonstrating squamous differentiation. One patient died within 3 months of presentation. Three patients survived for approximately 18 months each; two received chemotherapy but one was treated by surgical resection alone. The fifth patient had a peripheral coin lesion which was treated by surgical resection only; he is alive without evidence of recurrent carcinoma 1 year after operation. We suggest that some carcinomas of the lung with the light-microscopic and cytologic appearance of small cell anaplastic carcinoma are actually small cell variants of squamous cell carcinoma and lack the characteristic neurosecretory granules of classic small cell carcinoma. The behavior of these tumors needs to be determined.