Computer-aided diagnoses: automatic detection of lung nodules

This work describes a computational scheme for automatic detection of suspected lung nodules in a chest radiograph. A knowledge-based system extracts the lung masks over which we will apply the nodule detection process. First we obtain the normalized cross-correlation image. Next we detect suspicious regions by assuming a threshold. We examine the suspicious regions using a variable threshold which results in the growth of the suspicious areas and an increase in false positives. We reduce the large number of false positives by applying the facet model to the suspicious regions of the image. An algorithmic classification process gives a confidence factor that a suspicious region is a nodule. Five chest images containing 30 known nodules were used as a training set. We evaluated the system by analyzing 30 chest images with 40 confirmed nodules of varying contrast and size located in various parts of the lungs. The system detected 100% of the nodules with a mean of six false positives per image. The accuracy and specificity were 96%.     

Computer-aided diagnosis in chest radiography. Preliminary experience

RATIONALE AND OBJECTIVES: Computer-aided diagnosis (CAD) schemes for chest radiography are being developed with which to alert radiologists to possible lesions, and thus potentially improve diagnostic accuracy. However, CAD schemes have not been tested on a large number of clinical cases. The authors identify design parameters that would be required for development of an intelligent workstation. METHODS: Computer-aided diagnosis programs were applied for the automated detection of lung nodules, cardiomegaly, and interstitial infiltrates to 310 consecutive chest radiographs, and were analyzed for potential usefulness and limitations. Computer-aided diagnosis output was evaluated by radiologists and physicists for accuracy and technical problems, respectively. RESULTS: Approximately 70% of the results were judged to be potentially acceptable; however, the number of false-positive findings was relatively high. Technical problems included failure to detect subtle abnormalities and the occurrence of false-positive detections caused by normal anatomical structures. CONCLUSION: Computer-aided diagnosis has the potential to be a valuable aid to radiologists in clinical practice, if certain technical problems can be overcome and if optimal operating points can be defined for clinical use.     

Computer-aided diagnosis for interstitial infiltrates in chest radiographs: optical-density dependence of texture measures

We have been developing a computerized scheme for automated detection and characterization of interstitial infiltrates based on the Fourier transform of lung texture. To improve the performance of the scheme, which was developed using digitized screen-film radiographs, optical-density dependence of both the gradient of the film used and the system noise associated with the laser scanner were investigated. Two hundred chest radiographs, including 100 abnormal cases with interstitial infiltrates, were digitized using a laser scanner. The root-mean-square (RMS) variations and the first moments of the power spectra, which correspond to the magnitude and coarseness of lung texture, were determined by Fourier transform of lung textures in numerous regions of interest (ROIs). The RMS variation was dependent upon the average optical density in the ROI, though no obvious trend existed for the first moment of the power spectrum. Dependence of the RMS variations on optical density was corrected for using the gradient curve of the film. Also, system noise associated with the laser scanner was corrected. Results indicated that the specificity was improved from 81% (without correction) to 89% (with corrections), without any loss of sensitivity (90%). Thus, the correspondence between the computer output and consensus interpretation of radiologists was improved with the new scheme compared to the previous one. This improved computerized scheme may be useful to radiologists in detecting interstitial infiltrates in chest radiographs.     

Automated detection of clustered microcalcifications on mammograms: CAD system application to MIAS database

To investigate the detection performance of our automated detection scheme for clustered microcalcifications on mammograms, we applied our computer-aided diagnosis (CAD) system to the database of the Mammographic Image Analysis Society (MIAS) in the UK. Forty-three mammograms from this database were used in this study. In our scheme, the breast regions were firstly extracted by determining the skinline. Histograms of the original images were used to extract the high-density area within the breast region as the segmentation from the fatty area around the skinline. Then the contrast correction technique was employed. Gradient vectors of the image density were calculated on the contrast corrected images. To extract the specific features of the pattern of the microcalcifications, triple-ring filter analysis was employed. A variable-ring filter was used for more accurate detection after the triple-ring filter. The features of the detected candidate areas were then characterized by feature analysis. The areas which satisfied the characteristics and specific terms were classified and displayed as clusters. As a result, the sensitivity was 95.8% with the false-positive rate at 1.8 clusters per image. This demonstrates that the automated detection of clustered microcalcifications in our CAD system is reliable as an aid to radiologists.     

Application of artificial neural networks for quantitative analysis of image data in chest radiographs for detection of interstitial lung disease

The authors have developed an automated computeraided diagnostic (CAD) scheme by using artificial neural networks (ANNs) on quantitative analysis of image data. Three separate ANNs were applied for detection of interstitial disease on digitized chest images. The first ANN was trained with horizontal profiles in regions of interest (ROIs) selected from normal and abnormal chest radiographs for distinguishing between normal and abnormal patterns. For training and testing of the second ANN, the vertical output patterns obtained from the 1st ANN were used for each ROI. The output value of the second ANN was used to distinguish between normal and abnormal ROIs with interstitial infiltrates. If the ratio of the number of abnormal ROIs to the total number of all ROIs in a chest image was greater than a specified threshold level, the image was classified as abnormal. In addition, the third ANN was applied to distinguish between normal and abnormal chest images. The combination of the rule-based method and the third ANN also was applied to the classification between normal and abnormal chest images. The performance of the ANNs was evaluated by means of receiver operating characteristic (ROC) analysis. The average Az value (area under the ROC curve) for distinguishing between normal and abnormal cases was 0.976 +/- 0.012 for 100 chest radiographs that were not used in training of ANNs. The results indicate that the ANN trained with image data can learn some statistical properties associated with interstitial infiltrates in chest radiographs.     

Computerized analysis of interstitial disease in chest radiographs: improvement of geometric-pattern feature analysis

We have been developing automated computerized schemes to assist radiologists in interpreting chest radiographs for interstitial disease based on texture analysis and geometric-pattern feature analysis. In this study, we attempted to improve the performance of the geometric-pattern feature analysis, because the current classification performance with geometric-pattern feature analysis is considerably lower than that of texture analysis. In order to improve the performance in distinguishing between normal lungs and abnormal lungs with interstitial disease, we attempted to remove rib edges in regions of interest (ROIs) by using an edge detection technique, and also to reduce false positives by using feature analysis techniques. In addition, the effects of many parameters on classification performance were investigated to identify proper threshold levels, and subsequently the specificity of the geometric-pattern feature analysis was improved from 69.5% to 86.1% at a sensitivity of 95.0%. Using a combined rule-based method with texture analysis and geometric-pattern feature analysis plus the artificial neural network (ANN) method for classification, a high specificity of 96.1% was obtained at a sensitivity of 95.0%.     

Computerized detection of masses in digitized mammograms using single-image segmentation and a multilayer topographic feature analysis

RATIONALE AND OBJECTIVES: We developed and evaluated a computer-aided detection (CAD) scheme for masses in digitized mammograms. METHODS: A multistep CAD scheme was developed and tested. The method uses a technique of single-image segmentation with Gaussian bandpass filtering to yield a high sensitivity for mass detection. A rule-based multilayer topographic feature analysis method is then used to classify suspected regions. A set of 260 cases, including 162 verified masses, was divided into two subsets; one set was used to set the rule-based classification and one was used to test the performance of the scheme. RESULTS: In a preliminary clinical study, the implemented detection scheme yielded 98% sensitivity with a false-positive detection rate of less than one false-positive region per image. CONCLUSION: Single-image segmentation methods seem to have high sensitivity in selecting true-positive mass regions in the first stage of a CAD scheme. A multilayer topographic image feature analysis method in the second stage of a CAD scheme has the potential to significantly reduce the false-positive detection rate.     

Optimally weighted wavelet transform based on supervised training for detection of microcalcifications in digital mammograms

We are developing a computer-aided diagnosis (CAD) scheme for detection of clustered microcalcifications in digital mammograms. The use of an empirically chosen wavelet and scale combination for detection of microcalcifications as an initial step of the CAD scheme has been reported by us previously. In this study, we developed a technique for optimizing the weights at individual scales in the wavelet transform to improve the performance of our CAD scheme based on the supervised learning method. In the learning process, an error function was formulated to represent the difference between a desired output and the reconstructed image obtained from weighted wavelet coefficients for a given mammogram. The error function was then minimized by modifying the weights for wavelet coefficients by means of a conjugate gradient algorithm. The Least Asymmetric Daubechies' wavelets were optimized with 297 regions of interest (ROIs) as a training set by a jackknife method. The performance of the optimally weighted wavelets was evaluated by means of receiver-operating characteristic (ROC) analysis by use of the above set of ROIs. The analysis yielded an average area under the ROC curve of 0.92, which outperforms the difference-image technique used in our existing CAD scheme, as well as the partial reconstruction method used in our previous study.     

Cardiorespiratory responses to acute hypoxemia in the chronically catheterized fetal llama at 0.7-0.9 of gestation

PURPOSE: To compare hard-copy digital chest radiographs obtained with a selenium-based system with wide-latitude asymmetric screen-film radiographs for detection of pulmonary nodules. MATERIALS AND METHODS: Fifty patients undergoing thoracic computed tomography (CT) for suspected pulmonary nodules were recruited to undergo both digital and screen-film posteroanterior (PA) and lateral chest radiography. Three chest radiologists blinded to the CT results independently reviewed each digital and screen-film radiograph, identified each nodule, and graded their confidence for its presence. RESULTS: Seventy-eight pulmonary nodules (mean diameter, 1.5 cm; range, 0.5-3.5 cm; 62 soft tissue, 16 calcified) were identified with CT in 34 patients, while 16 patients had clear lungs. The mean sensitivity for the detection of all nodules by all readers (PA and lateral) was 66% (95% Cl, 54%, 76%) for digital radiographs and 64% (95% Cl, 52%, 74%) for screen-film radiographs. Differences between the two techniques were not statistically significant (P > .05, Student t test). There was no difference in mean false-positive-true-positive ratios (PA, 0.35; lateral, 0.53) or positive predictive values (PA, 74%; lateral, 65%), and no significant difference (P > .05) was seen in mean reader confidence rating. CONCLUSION: In detecting pulmonary nodules, radiologists perform comparably with selenium-based digital and wide-latitude asymmetric screen-film radiographs.     

An improved shift-invariant artificial neural network for computerized detection of clustered microcalcifications in digital mammograms

A shift-invariant artificial neutral network (SIANN) has been applied to eliminate the false-positive detections reported by a rule-based computer aided-diagnosis (CAD) scheme developed in our laboratory. Regions of interest (ROIs) were selected around the centers of the rule-based CAD detections and analyzed by the SIANN. In our previous study, background-trend correction and pixel-value normalization were used as the preprocessing of the ROIs prior to the SIANN. A ROI is classified as a positive ROI, if the total number of microcalcifications detected in the ROI is greater than a certain number. In this study, modifications were made to improve the performance of the SIANN. First, the preprocessing is removed because the result of the background-trend correction is affected by the size of ROIs. Second, image-feature analysis is employed to the output of the SIANN in an effort to eliminate some of the false detections by the SIANN. In order to train the SIANN to detect microcalcifications and also to extract image features of microcalcifications, the zero-mean-weight constraint and training-free-zone techniques have been developed. A cross-validation training method was also applied to avoid the overtraining problem. The performance of the SIANN was evaluated by means of ROC analysis using a database of 39 mammograms for training and 50 different mammograms for testing. The analysis yielded an average area under the ROC curve (A(z)) of 0.90 for the testing set. Approximately 62% of false-positive clusters detected by the rule-based scheme were eliminated without any loss of the true-positive clusters by using the improved SIANN with image feature analysis techniques.     

Identification of clustered microcalcifications on digitized mammograms using morphology and topography-based computer-aided detection schemes. A preliminary experiment

RATIONALE AND OBJECTIVES: A mathematical morphology-based computer-aided detection (CAD) scheme for the identification of clustered microcalcifications was developed and tested. The potential for improving either sensitivity or specificity by combining the results with those previously reported was investigated. METHODS: The CAD scheme presented here is based on mathematical morphology and a series of simple rule-based criteria for the identification of clustered microcalcifications. A database of 105 digitized mammograms was used for training and rule setting of the scheme. A test set of 191 digitized mammograms was used to evaluate its performance. The same test set had been used to evaluate a multilayer, topography-based scheme. The results obtained by the two schemes were then combined using logical OR and AND operations. RESULTS: The morphology-based and topography-based CAD schemes performed at sensitivities of 82.9% and 89.5%, with false-positive detection rates of 1.3 and 0.4 per image, respectively. A logical OR operation resulted in 95.4% sensitivity. An AND operation achieved 76.2% sensitivity, with no false identifications on 93% of images. CONCLUSIONS: By combining the results of the morphology-based and the topography-based schemes, either sensitivity or specificity can be improved.     

Clinical evaluation of single-exposure dual-energy subtraction chest radiography: with FCR 9501 ES]

Using the one-shot energy subtraction method, we took chest radiography of 1,031 outpatients of Kanazawa University Hospital. Chest radiographs were taken with the FCR 9501 ES system, with patients upright. We studied the clinical efficacy of this diagnostic method. The method and usage procedures involved have been sufficiently technologically refined to permit handling of an adequate number of patients in a reasonable time at a permissible exposure dose. However, the system can be further improved technologically in order to obtain fully consistent high-quality images, regardless of the patient's physique. For well-rounded image reading, three kinds of images must be generated simultaneously: an original image; soft tissue (bone subtracted image) and bone (soft tissue subtracted image) Some soft tissue image were helpful for detecting non-calcified parenchymal nodules that overlapped the rib shadow, and some bone image served to precisely diagnose the existence of abnormal ribs, calcified lymph nodes, and calcified nodules. Furthermore, the bone images were helpful for revealing that the fine infiltrative shadows in the lung fields in original images were actually pleural calcifications and that the poorly defined nodular opacities were, in reality, abnormal rib calcifications. In light of the above, we wish to stress the importance of clinical efficacy of not only soft tissue images but bone images derived using the energy subtraction method. The clinical usefulness of this method was confirmed in 66 of 1,031 patients (6.4%) who had initially been scheduled for routine chest radiography. This result indicates how frequently the method encounters applicable cases when applied non-selectively to general patients who require radiographic chest examination. The advantages of this method will become much more evident with an examination protocol that minimizes unnecessary special examinations or optimizes the balance between screening and special examinations.     

Viewing another person's eye movements improves identification of pulmonary nodules in chest x-ray inspection.

Double reading of chest x-rays is often used to ensure that fewer abnormalities are missed, but very little is known about how the search behavior of others affects observer performance. A series of experiments investigated whether radiographers benefit from knowing where another person looked for pulmonary nodules, and whether the expertise of the model providing the search behavior was a contributing factor. Experiment 1 compared the diagnostic performance of novice and experienced radiographers examining chest x-rays and found that both groups performed better when shown the search behavior of either a novice radiographer or an expert radiologist. Experiment 2 established that benefits in performance only arose when the eye movements shown were related to the search for nodules; however, only the novices' diagnostic performance consistently improved when shown the expert's search behavior. Experiment 3 reexamined the contribution of task, image, and the expertise of the model underlying this benefit. Consistent with Experiment 1, novice radiographers were better at identifying nodules when shown either a na?ve's search behavior or an expert radiologist's search behavior, but they demonstrated no improvement when shown a na?ve model not searching for nodules. Our results suggest that although the benefits of this form of attentional guidance may be short-lived, novices can scaffold their decisions based on the search behavior of others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of pregnancy outcome after intracytoplasmic sperm injection and in-vitro fertilization

BACKGROUND: The prognosis of patients with lung cancer is better when the diagnosis is made early; the disease is localized, and radical surgery is possible. Screening for lung cancer with mass radiography or sputum cytology should contribute to a more favorable prognosis. Large-scale screening studies have improved the survival rates for lung cancer but have yielded no reduction in mortality rates. METHODS: The histologic types, stages, treatments, and survival rates were studied in 93 men who were found to have lung cancer in a single chest radiograph screening of more than 33,000 men who smoked and were 50 to 69 years old ("screened cases"), and in 239 men of the same age range whose lung cancer was detected through ordinary health care system ("other cases") during the screening period. RESULTS: The distribution of the histology was similar in the two groups, but screening detected more instances of early-stage disease that were resectable more often than in the other group (37 vs 19%). The 5-year survival rate for men in the screened cases was 19%, and that of men in the other cases was 10% (relative risk, 0.65; 95% confidence interval [CI], 0.50 to 0.84). The survival rate of men in the screened cases remained significantly higher than that of men in the other cases even after adjustments for age, smoking status, histology, stage of the disease, and resectability of the disease (relative risk, 0.74; 95% CI, 0.55 to 1.00). CONCLUSIONS: According to this study, chest radiograph screening might improve the prognosis of lung cancer. Our results are, however, subject to many factors that were only partially controlled for, and they should be interpreted cautiously.     

Use of chest computed tomography in the staging of pediatric Wilms' tumor: interobserver variability and prognostic significance

PURPOSE: To determine the specificity and prognostic significance of computed tomography (CT) of the chest in pediatric Wilms' tumor. PATIENTS AND METHODS: Patients treated for newly diagnosed Wilms' tumor at St Jude Children's Research Hospital between December 1978 and July 1995 were included in the study if an initial chest radiograph and CT were available and if pulmonary involvement (determined by chest radiographs) was absent. For the 202 patients studied, radiographs and CT scans were reviewed blindly and independently by three experienced radiologists for the presence of pulmonary nodules. Outcome variables consisted of intraobserver variability (in a subsample of 40 cases) and concordance between ratings on radiographs and CT scans (both by McNemar's test), interrater variability (by logistic regression), and the cumulative incidence of pulmonary relapse for patients with and without positive CT scans, by reviewer. RESULTS: As expected, ratings of pulmonary involvement on radiographs were discordant with CT ratings. There was marked variability among reviewers in CT ratings (P = .0001). Of 202 CT scans, 78 were read as positive by at least one reviewer, 41 were rated positive by only one reviewer, 18 by two reviewers, and 19 by all three. Intrarater variability on repeat reviews was not significant. Patients with nodules identified on CT had a significantly higher pulmonary relapse rate when analyzed separately by reviewer. However, for the 14 patients who had pulmonary relapse, CT scans were rated positive by all three reviewers in only five cases and as negative by all three in another five cases. CONCLUSION: The variability in interpretation of chest CT scans in patients with Wilms' tumor limits the predictive utility of these studies. Optimal, standardized techniques and central review are essential if chest CT is to be used for staging in cooperative studies.     

Depot medroxyprogesterone acetate or oral contraception in postpartum adolescents

The purpose of the study was the evaluation of low-dose spiral CT in the detection and assessment of contours of pulmonary nodules. In a prospective investigation 71 consecutive chest CT examinations were acquired both at 30 and 200 mA. Films were interpreted independently by two radiologists. According to the size, nodules were divided into four categories: 10 mm; nodule shape was registered. With both protocols, 240 nodules were detected. The correlation coefficient for both methods was 0.89. Discrepancies were found most frequently in nodules near to pulmonary vessels. Nodule size estimation did not differ more than one size category. Eight spiculated nodules were identified by both techniques. Low-dose spiral CT of the chest has a high sensitivity in the detection of pulmonary nodules. If clinical circumstances require dose minimization, low-dose spiral CT may be advocated as an alternative screening method to conventional dose spiral CT.     

Grid versus non-grid techniques for the detection of pulmonary nodules in a chest phantom

A partial chest phantom was constructed to compare two commonly employed radiographic techniques, 70 kVp without a grid and 120 kVp with a grid, for the detection of pulmonary nodules. The phantom consisted of human ribs embedded in paraffin, the lungs of a dog injected with silicone rubber, a tissue equivalent wax heart and beeswax nodules. The nodules ranged in size from 3-7 mm. A series of 120 films was exposed, half with each technique, and the films were interpreted by three senior residents and seven staff radiologists. More nodules of all sizes except 3 mm were detected with the 120 kVp technique. The 3 mm nodules were rarely detected with either technique. The disadvantages of the 120 kVp technique were an approximate 50 percent increase in patient exposures and almost twice as many false-positive nodule detections.     

Is the chest radiograph a reliable tool in the assessment of tumor response after radiotherapy in nonsmall cell lung carcinoma?

BACKGROUND: The purpose of this study was to evaluate whether the chest radiograph is a reliable tool to assess response to radiotherapy. MATERIALS AND METHODS: Pre- and post-treatment chest radiographs and computed tomographs (CT) of 63 patients with nonsmall cell lung cancer (NSCLC) treated by radiotherapy were reviewed by four observers with regard to suitability for tumor measurement, and response. Suitability for tumor measurement was expressed as the number of measurable diameters. In addition, the consequences to clinical outcome were studied by survival analysis. RESULTS: The CT turned out to be more suited for tumor measurement before as well as after radiotherapy, resulting in an increase of the number of measurable cases. The number of measurable cases with CT was 52 (83%) as compared to 28 (44%) with chest radiography. Especially in case of centrally localized tumors, the presence of an atelectasis, or squamous cell carcinoma, CT contributed to a higher rate of measurable cases. The interobserver agreement with regard to response using chest radiograph was good (mean kappa = 0.74). In 25 of 28 cases (89%) measurable with CT as well as with chest radiograph, response was equally classified. When CT was used, the median survival of the responders was 14.2 months as compared to 6.8 months of the nonresponders. When chest radiograph was used, the median survival of these groups was 12.0 and 6.6 months respectively, which was not significantly different when response was assessed by CT. CONCLUSION: We conclude that CT is more suited for tumor measurement because more measurable lesions can be found and more evaluable lesions on chest radiograph become measurable on CT. The chest radiograph does have a valuable role to play in those lesions that are measurable because of the good interobserver agreement with regard to the response classification, the high overall agreement between CT and chest radiograph in case of measurable cases, and the lack of important differences with regard to survival.     

Dipyridamole stress echocardiography for risk stratification in hypertensive patients with chest pain

BACKGROUND: The noninvasive prognostic assessment of coronary artery disease (CAD) in hypertensive patients represents an unresolved task to date. In this study, we investigated the value of dipyridamole stress echocardiography in risk stratification of hypertensive patients with chest pain and unknown CAD. METHODS AND RESULTS: Dipyridamole stress echocardiography was performed in 257 hypertensives (110 men; age, 63+/-9 years) complaining of chest pain and without a history of CAD. No major complications occurred. Four tests were interrupted prematurely because of side effects, with 98. 4% feasibility of test. A positive echocardiographic response was found in 72 patients (27 during the low-dose [0.56 mg/kg]). During the follow-up (32+/-18 months), 27 cardiac events occurred: 3 deaths, 8 infarctions, and 16 cases of unstable angina. Moreover, 27 patients underwent coronary revascularization. At multivariate analysis, the positive echocardiographic result (OR, 5.5; 95% CI, 1.4 to 16.6) was the only predictor of hard cardiac events (death, infarction). Considering spontaneous cardiac events (death, infarction, and unstable angina) as end points, the positive echocardiographic result (OR, 4.2; 95% CI, 1.8 to 9.6) and family history of CAD (OR, 4.2; 95% CI, 1.5 to 6. 9) were independently associated with prognosis. The 3-year survival rates for the negative and the positive populations were, respectively, 97% and 87% (P=0.0019) considering hard cardiac events and 96% and 74% (P=0.0000) considering spontaneous cardiac events. CONCLUSIONS: Dipyridamole stress echocardiography is safe, highly feasible, and effective in risk stratification of hypertensives with chest pain and unknown CAD. At present, it represents an attractive option for prognostic assessment of this clinically defined population.     

Lung cancer in patients with HIV-infection

PURPOSE: To identify and review the clinical characteristics and natural history of lung cancer in HIV-seropositive patients. A secondary objective was to compare the clinical features of HIV-seropositive and HIV-indeterminate lung cancer cases at our institution. PATIENTS AND METHODS: Sixteen patients with HIV infection and lung cancer were diagnosed between January 1988 and March 1995 at our institution and the clinical records were reviewed. HIV-indeterminate lung cancer cases were identified by the Albany Medical Center Hospital (AMCH) Tumor Registry. A Medline database search of HIV infection/AIDS and lung cancer was undertaken through December 1994. The New York State Department of Health (NYSDOH), Bureau of Cancer Epidemiology provided information on the incidence of lung cancer among residents of New York State by county of residence. Case reports and series regarding the clinical features of HIV-seropositive patients with lung cancer were reviewed. A more focused comparison between HIV-seropositive and HIV-indeterminate male lung cancer cases between 35 and 54 years of age at our institution was performed. The following clinical variables were identified in our 16 patients and 109 cases extracted from available clinical reports: sex, age, year and county of residence at time of lung cancer diagnosis, cigarette smoking history, HIV risk behavior, CD4 count at time of lung cancer diagnosis, CDC classification of HIV disease, interval in months from time of HIV seropositivity to lung cancer diagnosis, pathology and stage of lung cancer, performance status, treatment, response, and survival. RESULTS: Lung cancer in HIV-seropositive patients is characterized by the following: a younger age at time of diagnosis when compared to HIV-indeterminate cases; the majority of cases occur in a background of extensive cigarette smoking; over 80% of patients present with advanced stage of lung cancer (stage III and IV); up to 50% of cases have asymptomatic to mildly symptomatic HIV infection with a median CD4 lymphocyte count of 233 per microliter; there is a predominance of adenocarcinoma histopathology; and shortened survival when compared to HIV-indeterminate cases. CONCLUSION: Current reports of lung carcinoma in HIV-seropositive patients suggest that the natural history of this disease is different than in HIV-indeterminate cases. Lung cancer must be considered in the differential diagnosis of a solitary mass lesion on chest X-ray in HIV-seropositive patients.