Prognostic gene expression signature for high-grade serous ovarian cancer.

BACKGROUND: Median overall survival (OS) for women with high-grade serous ovarian cancer (HGSOC) is ∼4 years, yet survival varies widely between patients. There are no well-established, gene expression signatures associated with prognosis. The aim of this study was to develop a robust prognostic signature for OS in patients with HGSOC. PATIENTS AND METHODS: Expression of 513 genes, selected from a meta-analysis of 1455 tumours and other candidates, was measured using NanoString technology from formalin-fixed paraffin-embedded tumour tissue collected from 3769 women with HGSOC from multiple studies. Elastic net regularization for survival analysis was applied to develop a prognostic model for 5-year OS, trained on 2702 tumours from 15 studies and evaluated on an independent set of 1067 tumours from six studies. RESULTS: Expression levels of 276 genes were associated with OS (false discovery rate < 0.05) in covariate-adjusted single-gene analyses. The top five genes were TAP1, ZFHX4, CXCL9, FBN1 and PTGER3 (P < 0.001). The best performing prognostic signature included 101 genes enriched in pathways with treatment implications. Each gain of one standard deviation in the gene expression score conferred a greater than twofold increase in risk of death [hazard ratio (HR) 2.35, 95% confidence interval (CI) 2.02-2.71; P < 0.001]. Median survival [HR (95% CI)] by gene expression score quintile was 9.5 (8.3 to -), 5.4 (4.6-7.0), 3.8 (3.3-4.6), 3.2 (2.9-3.7) and 2.3 (2.1-2.6) years. CONCLUSION: The OTTA-SPOT (Ovarian Tumor Tissue Analysis consortium - Stratified Prognosis of Ovarian Tumours) gene expression signature may improve risk stratification in clinical trials by identifying patients who are least likely to achieve 5-year survival. The identified novel genes associated with the outcome may also yield opportunities for the development of targeted therapeutic approaches.

Old versus new FIGO staging systems in predicting overall survival in patients with uterine leiomyosarcoma: a study of 86 cases.

OBJECTIVES: Uterine leiomyosarcoma (uLMS) was staged using the FIGO system for endometrial cancers. The new FIGO system takes into consideration tumor size disregarding myometrial and cervical involvement. We aimed to compare the two systems and see which more accurately predicts overall survival (OS). METHODS: 86 patients with uLMS (1984-2010) were retrospectively staged using both FIGO systems. Mean OS rates were estimated using the Kaplan-Meier method. RESULTS: More patients had stage-I disease by the new FIGO system (42 versus 33). Five versus 18 and 27 versus 5 had old and new stage-II and III diseases respectively. Five and 4 patients with old stage II and III uLMS respectively were downstaged to stage I while 18 with old stage III were downstaged to stage II. Median follow-up was 23.5 months with a median OS of 114 (95% CI, 61-166) months. Although patients with stage I tumors had a higher mean OS rate compared to those with higher stage disease by either system, patients with old stage II-IV disease showed similar mean OS rates, with stage III-IV patients having a slightly better mean OS and a similar trend was observed with the new system. Patients with new FIGO stage III had a higher mean OS rate than those with stage II or IV disease (37.6 versus 28.1 and 34.3 months). Nonetheless, no statistical significant differences were seen in OS according to stage using either system (p=0.786 and p=0.400 respectively). CONCLUSION: Neither FIGO staging system is ideal in classifying patients into four clinically significant stages.

Testing for her2 in breast cancer: current pathology challenges faced in Canada.

This review is designed to highlight several key challenges in the diagnosis of human epidermal growth factor receptor 2 (her2)-positive breast cancer currently faced by pathologists in Canada: Pre-analysis issues affecting the accuracy of her2 testing in non-excision sample types: core-needle biopsies, effusion samples, fine-needle aspirates, and bone metastasesher2 testing of core-needle biopsies compared with surgical specimensCriteria for retesting her2 status upon disease recurrenceLiterature searches for each topic were carried out using the medline, Embase, International Pharmaceutical Abstracts, and biosis databases. In addition, the congress databases of the American Society of Clinical Oncology (2005-2011) and the San Antonio Breast Cancer Symposium (2007-2011) were searched for relevant abstracts.All authors are expert breast pathologists with extensive experience of her2 testing, and several participated in the development of Canadian her2 testing guidelines. For each topic, the authors present an evaluation of the current data available for the guidance of pathology practice, with recommendations for the optimization or improvement of her2 testing practice.

Amyloidosis of the uterine cervix presenting as postmenopausal bleeding.

BACKGROUND: Amyloidosis of the uterine cervix is rare. CASE: A postmenopausal woman with systemic amyloidosis related to multiple myeloma presented with postmenopausal vaginal bleeding. CONCLUSION: This case illustrates the variable presentation of amyloidosis.

Spontaneous regression of stage IV clear cell carcinoma of the endometrium in a patient with essential thrombocytosis.

OBJECTIVE: The aim of this study was to document a case of advanced stage clear cell carcinoma of the endometrium which underwent spontaneous regression (SR) and comment on the possible contribution of the patient's thrombocytosis. CASE REPORT: A 73-year-old woman with essential thrombocytosis presented with vaginal bleeding. Imaging demonstrated a complex uterine mass, a 4-cm infrarenal mass, and a 5-cm subumbilical mass. Biopsy of the subumbilical mass revealed adenocarcinoma, and endometrial curettage revealed extensively necrotic clear cell endometrial carcinoma. At hysterectomy 5 weeks later, the infrarenal and subumbilical masses were not identified. The endometrial tumor was almost completely necrotic. She received no adjuvant therapy and remains disease-free 6 years later. Interestingly, her platelet-lowering agent (hydroxyurea) was discontinued shortly before, and her platelet count was significantly elevated at the time of her presentation with endometrial carcinoma. CONCLUSION: This report documents a rare case of SR of advanced endometrial carcinoma, and we speculate that increased circulating platelets were a major contributing factor.

Healed or quiescent temporal arteritis versus senescent changes in temporal artery biopsy specimens.

Temporal arteritis (TA) is a common idiopathic vasculitis of the elderly. It is controversial whether, in the absence of an active inflammatory process, vessel damage secondary to temporal arteritis is distinguishable from changes secondary to arteriosclerosis. The primary goal of this study was to attempt to differentiate microscopically between healed temporal arteritis and arteriosclerosis, in the absence of active vasculitis. This was a retrospective study in which 47 temporal artery biopsy specimens, done between 1981 and 1997 at University of British Columbia Hospital, were reviewed. As well, temporal arteries harvested from 10 autopsy cases with no clinical evidence of vasculitis were used as controls. Haematoxylin and Eosin and Movat's pentachrome stains were used to assess the degree of intimal thickening, presence or absence of inflammation, type of inflammatory cell(s), the degree of reduplication of elastic lamina, calcification, fibrosis, neovascularisation and gaps or losses in the internal and external elastic lamina. No histological findings were specific for temporal arteritis except the presence of mural inflammation. A high degree of variability existed for all other features assessed, within all groups studied. These results indicate that, in the absence of active inflammation, structural changes in the vessel wall do not allow reliable differentiation between healed or quiescent temporal arteritis and arteriosclerosis. The common practice of performing special stains in all temporal artery biopsy cases does not contribute to the ability to recognise temporal arteritis.

Early stage uterine papillary serous carcinoma of the endometrium: effect of adjuvant whole abdominal radiotherapy and pathologic parameters on outcome.

BACKGROUND: Uterine papillary serous carcinoma (UPSC) is an aggressive subtype of endometrial cancer, behaving like ovarian epithelial cancers and having a predilection for transperitoneal relapse. Within this subtype of uterine cancers, predictors of outcome and the role of adjuvant therapies have not been firmly established, to the authors' knowledge. METHODS: Between 1985-1995, 78 patients who had International Federation of Gynecology and Obstetrics (FIGO) Stage I, II, or IIIa UPSC (based on positive washings only) were seen at the British Columbia Cancer Agency. During this time, the authors had a policy of offering adjuvant pelvic, paraaortic and whole-abdominal radiotherapy (WART) to these patients. Fifty-eight patients received adjuvant WART, and 20 received lesser or no adjuvant therapy. The authors undertook a retrospective analysis of pathology with quantification of the percentage of papillary serous component (% PSC) and p53 expression. Pathology was retrieved and reviewed on 62 patients; p53 staining was performed on blocks from the hysterectomy specimen in 46 cases. Pathologic parameters, stage, and adjuvant therapy were correlated with clinical outcome in a multivariate analysis. RESULTS: Median follow-up was 52 months (3-139 mos) and the 5-year disease-specific survival rate was 66.2%. The 58 patients who received adjuvant WART had a significantly better 5-year disease-specific survival than those 20 patients who did not, 74.9% versus 41.3% (P = 0.04). Multivariate analysis showed that % PSC and p53 were not significant predictors of outcome for early stage UPSC. Of the factors examined, only FIGO stage and WART significantly predicted improved outcome (P = 0.02 and 0.04, respectively). CONCLUSIONS: The current study demonstrated a significant difference in the outcomes of patients who had FIGO Stage I compared with Stage II UPSC. In the current series of patients, the authors were not able to predict outcome based on % PSC or p53 expression. The current study results with WART were promising, and WART merits further study.

The separation of benign and malignant mesothelial proliferations.

The separation of benign from malignant mesothelial proliferations has emerged as a major problem in the pathology of the serosal membranes. For both epithelial and spindle cell mesothelial processes, true stromal invasion is the most accurate indicator of malignancy, but stromal invasion is often difficult to assess, especially in small biopsies. In the pleural cavity, deep penetration of a thickened and fibrotic pleura or penetration of mesothelial cells into the fat of the chest wall are good indicators of malignancy; however, superficial entrapment of mesothelial cells and glands by organizing effusions is common in benign reactions and needs to be distinguished from invasion. In the peritoneal cavity, invasion of fat or of organ walls is again the most reliable indicator of malignancy, but entrapment of benign cells in organizing granulation tissue or between fat lobules is frequent and confusing. Proliferations confined to the pleural or peritoneal space, particularly linear arrays of atypical mesothelial cells on the free surface, should not be called malignant in the absence of unequivocal invasion. Cytologic atypia is often not helpful in separating benign from malignant reactions, because benign processes are commonly atypical and mesotheliomas are often deceptively monotonous. Densely packed mesothelial cells within the pleural space are frequent in benign reactions, but densely packed mesothelial cells within the stroma favor a diagnosis of malignancy. Organizing effusions (fibrous pleurisy) typically show zonation with high cellularity and cytologic atypia toward the pleural space and increasing fibrosis with decreasing cellularity and lesser atypia toward the chest wall, whereas sarcomatous (including desmoplastic) mesotheliomas do not demonstrate this type of zonation. Elongated capillaries perpendicular to the pleural surface are seen in organizing effusions but are not a feature of sarcomatous mesotheliomas. The combination of a paucicellular storiform pattern, plus invasion of the stroma (including fat and adjacent tissues), or bland necrosis, overtly sarcomatous foci, or distant metastases, is required for the diagnosis of desmoplastic mesothelioma. Necrosis is usually a sign of malignancy but is occasionally seen in benign mesothelial reactions. Keratin staining is useful in indicating the distribution of mesothelial cells, and particularly in demonstrating penetration of mesothelial cells into the stroma or adjacent structures, but is of no help in separating benign and malignant proliferations because both are keratin-positive. Although both p53 and EMA staining have been proposed as markers of mesothelial malignancy, in our experience they are not helpful for the individual case.

Acute cigarette smoke-induced connective tissue breakdown is mediated by neutrophils and prevented by alpha1-antitrypsin.

Recent studies have suggested that macrophage-derived metalloproteases are the critical mediators of cigarette smoke-induced emphysema, in contrast to earlier hypotheses that this process was mediated by neutrophil elastase. To determine whether smoke can acutely induce connective tissue breakdown in the lung and to examine the mediators of this process, we exposed C57-BL/6 mice to whole cigarette smoke and used high-performance liquid chromatography to examine lavage fluid levels of desmosine (DES), a marker of elastin breakdown, and hydroxyproline (HP), a marker of collagen breakdown. Smoke produced a dose-response increase in lavage neutrophils, DES, and HP, but not lavage macrophages (MACs). This effect was evident by 6 h after exposure to two cigarettes. Pretreatment with an antibody against polymorphonuclear leukocytes (PMNs) reduced lavage PMNs to undetectable levels after smoke exposure, did not affect MAC numbers, and prevented increases in lavage DES and HP. Intraperitoneal injection of a commercial human alpha1-antitrypsin (alpha1AT) 24 h before smoke exposure increased serum alpha1AT levels approximately 3-fold and completely abolished smoke-induced connective tissue breakdown as well as the increase in lavage PMNs, again without affecting MAC numbers. We conclude that in this model cigarette smoke can acutely induce connective tissue breakdown and that this effect is mediated by neutrophil-derived serine proteases, most likely neutrophil elastase. Exogenous alpha1AT is protective and appears to inhibit both matrix degradation and PMN influx, suggesting that alpha1AT has anti-inflammatory as well as antiproteolytic effects in this system.

Pathogenesis of Fibrosis Produced by Asbestos and Man-Made Mineral Fibers: What Makes a Fiber Fibrogenic?

Recent studies have revealed a wide array of molecular and cellular changes in cells and whole lungs exposed to asbestos fibers, changes that are presumed to be related to asbestos-induced fibrogenesis. These include generation of reactive oxygen species (ROS), induction of cell signaling factors and proinflammatory cytokines, and induction of fibrogenic mediators. Tumor necrosis factor-alpha (TNFα) appears to play a crucial role, since mice with TNFα receptor genes knocked out are resistant to asbestos-induced fibrosis. However, many man-made mineral fibers (MMVF) are able to generate ROS, cell signaling factors, and proinflammatory cytokines (probably every fiber causes expression of TNFα), but there is no clear correlation between the ability of MMVF to initiate these events and their ability to produce fibrosis. Moreover, asbestos produces fibrosis in tracheal explant systems without increasing TNFα expression, and nonfibrogenic dusts induce fibrogenic mediators such as transforming growth factor-beta (TCFß) and platelet-derived growth factor (PDGF) but not procollagen in such systems. It remains uncertain whether alveolar macrophages are central to fibrosis, as is often assumed, or whether fibers penetrating tissue are the real effector agents. Fiber length, biopersistence, and dose clearly do play a very important role in fibrogenesis, since short fibers, readily degraded fibers, and small numbers of fibers of any type are nonfibrogenic. There is some evidence to suggest that short and nonpersistent fibers produce quantitatively less of the mediators just described, but the ability of macrophages to clear fibers is probably crucial to preventing fibrosis. Thus, molecular and cellular events must combine in as yet uncertain ways with abnormalities at a more "'macroscopic" level before fibrosis can become established.

Induction of fibrogenic mediators by fine and ultrafine titanium dioxide in rat tracheal explants.

Respirable ambient particles [particulate matter <10 micrometer (PM(10))] are associated with both acute and chronic adverse health effects including chronic airflow obstruction. PM(10) can induce expression of inflammatory and fibrogenic mediators, but there is controversy about the types and/or sizes of particles involved and, in particular, whether ultrafine particles are the major toxic agents. To examine whether particle size affects mediator generation, we exposed rat tracheal explants, an inflammatory cell-free model of the airway wall, to various concentrations up to 500 microgram/cm(2) of fine (0.12 micrometer) or ultrafine (0.021 micrometer) titanium dioxide (anatase), maintained the explants in an organ culture in air for 1-7 days, and used RT-PCR to examine the expression of fibrogenic mediators and procollagen. No increase in gene expression was seen at 1 or 3 days, but at 5 days, ultrafine dust induced a small increase in procollagen. At 7 days, fine titanium dioxide produced significantly greater increases for platelet-derived growth factor (PDGF)-B, transforming growth factor-alpha, and transforming growth factor-beta compared with those by ultrafine dust; both dusts produced similar increases for PDGF-A; and ultrafine dust produced increases in procollagen expression, whereas fine dust had no effect. Expression levels were dose related. Both dusts produced a similar decrease in expression of PDGF receptor-alpha and a similar increase in PDGF receptor-beta. These observations suggest that ultrafine particles are intrinsically able to induce procollagen expression even in the absence of inflammatory cells; that chronic exposure to PM(10) may result in chronic airflow obstruction, in part because of ultrafine particle-mediated increases in airway wall fibrosis; and that chemically identical dusts of differing size can produce quite different patterns of gene expression in the airway wall. Differential upregulation of PDGF receptors does not appear to explain dust-induced fibrosis in this model.

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.

Mineral dusts directly induce epithelial and interstitial fibrogenic mediators and matrix components in the airway wall.

Exposure to mineral dusts is associated with the development of chronic airflow obstruction, probably mediated in part by dust-induced fibrosis of the small airways. To investigate the mechanism of fibrosis, we exposed rat tracheal explants to amosite asbestos, iron oxide, or titanium dioxide. Explants were then maintained in air organ culture, and the expression of genes encoding for various mediators and matrix components assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). At 7 d, all dusts produced significant increases in platelet-derived growth factor-A (PDGF-A) and transforming growth factor-beta1 (TGF-beta1) gene expression compared with control; asbestos and titanium dioxide produced increases in PDGF-B, and titanium dioxide increased TGF-alpha expression. Only asbestos caused increases in procollagen expression. No dust increased expression of tumor necrosis factor-alpha (TNF-alpha), fibronectin, or tropoelastin. Elevations in these factors coincided temporally with transport of particles into the epithelium and then to the subepithelial space. By in situ hybridization, TGF-beta gene expression was found in both the epithelium and subepithelial (interstitial) space, and PDGF-B and procollagen gene expression in the subepithelial space. Chemical analysis showed a small increase in hydroxyproline, a measure of collagen content, in asbestos-treated explants. We conclude that mineral dusts can induce airway wall fibrosis by directly upregulating proliferative and fibrogenic mediators as well as matrix components in the airway epithelium and interstitium, and that neither airspace nor circulating inflammatory cells are required for these effects. Different mineral dusts produce different patterns of reaction.

Rat mesothelial and tracheal epithelial cells show equal DNA sensitivity to hydrogen peroxide-induced oxidant injury.

To study the relative sensitivity of rat tracheal epithelial and mesothelial cell DNA to oxidant damage, we used the comet assay, a gel microelectrophoresis method that allows visual determination of DNA strand breaks on a cell-by-cell basis, to evaluate damage after hydrogen peroxide exposure. By both a qualitative and a quantitative assay, tracheal epithelial mesothelial cells demonstrated a similar dose-response increase in the number of cells showing strand breaks and the number of breaks per cell after exposure to increasing concentrations of hydrogen peroxide; but even at the highest concentration, some cells failed to show damage. By contrast, 100% of cultured V79 lung fibroblasts showed evidence of damage. Catalase and deferoxamine largely prevented the formation of strand breaks, while superoxide dismutase was not protective. To evaluate DNA repair, cells were exposed to 10 microM hydrogen peroxide for 10 min, washed, and maintained in culture medium; by 2 h the proportion of mesothelial and epithelial cells showing comets had returned to control levels for both cell types. Both cell types also showed a similar pattern of increasing damage after continuous exposure to 10 microM hydrogen peroxide for periods up to 2 h. We conclude that, in this system, 1) mesothelial and tracheobronchial epithelial cells show a similar pattern of DNA injury and repair after hydrogen peroxide exposure; 2) hydrogen peroxide damages DNA of both cell types via a mechanism probably related to the iron-catalyzed formation of hydroxyl radical; and 3) both types of cells appear to be heterogeneous in their sensitivity to oxidant damage, with some cells showing extreme resistance to such damage.

Spontaneous pulmonary hemorrhage after thrombolytic therapy for acute myocardial infarction.

We report a case of 63-year-old man who developed massive pulmonary hemorrhage following intravenous streptokinase for acute myocardial infarction. Pulmonary hemorrhage was diagnosed by the triad of hemoptysis, a drop in hematocrit, and a new unilateral infiltrate on chest radiograph. This diagnosis was confirmed by autopsy findings. Pulmonary hemorrhage has rarely been reported following thrombolytic therapy. We believe that pulmonary hemorrhage is a rare but a potentially life-threatening complication of thrombolytic therapy and should be considered in the differential diagnosis of pulmonary infiltrates or falling hemoglobin after thrombolytic therapy for acute myocardial infarction with no obvious site of bleeding.

Rapid short-term clearance of chrysotile compared with amosite asbestos in the guinea pig.

Compared with amphibole forms of asbestos, chrysotile asbestos fails to accumulate in lung tissue; the mechanism of this effect is disputed. To investigate this problem, we administered a mixture of the amphibole, amosite, and chrysotile to guinea pigs by intratracheal instillation. At 1 day, 1 week, and 1 month after instillation, animals were killed, and the numbers, types, sizes, and compositions of fibers in the lungs were determined by analytical electron microscopy. Both chrysotile and amosite fiber concentrations decreased with time, but relative chrysotile clearance was significantly greater than amosite clearance. There was no evidence of magnesium leaching from chrysotile fibers of any size at any time. Analysis of fiber lengths and widths showed a time trend toward shorter and narrower fibers (particularly toward fibers of less than 2 microns long and less than 0.025 microns wide) for chrysotile. This effect was not seen for amosite. We conclude that (1) failure of chrysotile accumulation in lung results from preferential chrysotile clearance during the first few days to weeks after exposure; (2) there is no evidence that fiber dissolution plays a role in chrysotile clearance; (3) preferential clearance may be a result of fragmentation and rapid removal of chrysotile fibers.

Coexistence of intracytoplasmic lumens and membrane-bound vesicles in an invasive carcinoma arising in a cystosarcoma phyllodes.

An unusual invasive breast carcinoma, arising in a cystosarcoma phyllodes and characterized by a variable cytoplasmic appearance and mucin content, was evaluated to determine the nature of the secretory material within the cells as well as the type of secretory organelle at the ultrastructural level. Histochemical studies revealed both acidic (sialic acid) and neutral mucin within the tumor cells. Ultrastructural analysis revealed secretory material within membrane-bound vesicles in some cells and within intracytoplasmic lumens in others; some cells contained both membrane-bound vesicles and intracytoplasmic lumens simultaneously. The Golgi derivation of the intracytoplasmic lumens was supported by their presence within or near hyperplastic Golgi complexes. The histochemical characteristics of the secretory material is correlated with their ultrastructural site of accumulation.

Sonographic appearance of normal intramammary lymph nodes.

Sonographic breast examinations were performed on 1030 patients with palpable or mammographically detected masses. In five cases, the lesions were normal intramammary lymph nodes. The ultrasonographic characteristics of this entity were confirmed by a sonographic/pathologic correlation study carried out on a cadaver axilla. Normal lymph nodes appeared as well-defined echo-poor masses with echogenic centers. In the absence of other suspicious lesions or proven malignant tumors, these nodes should be considered benign and not biopsied, but followed by repeat examinations.

Effects of cigarette smoke on tissue uptake and retention of iron oxide in the guinea pig.

We have previously shown that cigarette smoke increases retention and tissue penetration of asbestos, a pathogenic dust. To determine whether these same phenomena occur with an inert dust, we administered iron oxide particles to guinea pigs by intratracheal instillation. Half of the animals were exposed to cigarette smoke. Animals were killed at 1 day, 1 wk, and 1 month. Numbers of particles in airway epithelia and walls were counted in histologic sections of one lung, and the other lung was analyzed chemically for iron content. In both smoke-exposed and nonexposed groups, the chemically determined concentration of iron in the lung tissue decreased between 1 day and 1 month; however, the concentration of iron was significantly greater in the smoke-exposed group at 1 day and 1 wk. By 1 month, there was no significant difference between the 2 groups. The number of particles in the epithelia of respiratory bronchioles also decreased in both smoke-exposed and nonexposed groups between 1 day and 1 month, but the smoke-exposed group had significantly more intraepithelial particles at 1 day and 1 wk than did the nonexposed group. The number of particles in the walls of respiratory bronchioles increased between 1 day and 1 month in both smoke-exposed and nonexposed groups; the difference between these groups was significant only at 1 wk, when airway walls of the smoke-exposed animals contained more particles.(ABSTRACT TRUNCATED AT 250 WORDS)