High-resolution CT analysis of small peripheral lung adenocarcinomas revealed on screening helical CT

Management of an incidentally discovered pulmonary nodule

The incidental finding of a pulmonary nodule on computed tomography (CT) is becoming an increasingly frequent event. The discovery of such a nodule should evoke the possibility of a small bronchogenic carcinoma, for which excision is indicated without delay. However, invasive diagnostic procedures should be avoided in the case of a benign lesion. The objectives of this review article are: (1) to analyze the CT criteria defining benign nodules, nodules of high suspicion of malignancy and indeterminate nodules, (2) to analyze the diagnostic performances and limitations of complementary investigations requested to characterize indeterminate lung nodules, (3) to review the criteria permitting to assess the probability of malignancy of indeterminate nodules and (4) to report on the new guidelines provided by the Fleischner Society for the management of small indeterminate pulmonary nodules, according to their prior probability of malignancy.

CT screening for lung cancer: significance of diagnoses in its baseline cycle

PURPOSE

The aim of this study was to assess the significance of Stage I diagnoses of lung cancer in the baseline cycle of screening for this disease, with special reference to the potential for overdiagnosis.

METHODS

We reviewed all 69 cases of Stage I lung cancer diagnosis resulting from our baseline CT screening. Among these 69 cases of lung cancer, 24 presented as solid, 30 as part-solid, and 15 as nonsolid nodules. The extent to which these represented genuine malignancy was assessed by a panel of experts on lung pathology, and the "aggressiveness" of these cases was addressed by the criterion of the tumor's volume doubling time being less than 400 days.

RESULTS

The expert panel confirmed all 69 cases as representing genuine malignancy. Among the 69 cases without evidence of metastases, the proportion that satisfied the aggressiveness criterion was 60/69=87%. The corresponding proportions by presentation as solid, part-solid, and nonsolid nodule were 23/24 (96%), 27/30 (90%), and 10/15 (67%), respectively.

CONCLUSIONS

In baseline CT screening for lung cancer, overdiagnosis of the disease is uncommon, with cases presenting as a nonsolid nodule a possible exception to this.

Computer-aided diagnosis: a shape classification of pulmonary nodules imaged by high-resolution CT

We investigated the possibility of using computer analysis of high-resolution CT images to radiologically classify the shape of pulmonary nodules. Using a combination of circularity and second moment as quantitative measures we were able to classify pulmonary nodules in each shape group as effectively as could a radiologist. We found that pulmonary nodules with circularity < or =0.75 and second moment < or =0.18 were very likely to reveal lung cancer.

Focal area of ground-glass opacity and ground-glass opacity predominance on thin-section CT: Discrimination between neoplastic and non-neoplastic lesions

AIM

To reveal differences in thin-section computed tomography (CT) findings between lung neoplastic lesions and non-neoplastic lesions, which showed a focal area of ground-glass opacity or ground-glass opacity predominance.

MATERIALS AND METHODS

A total of 82 focal areas of ground-glass opacity and ground-glass opacity predominance, consisting of 38 neoplastic and 44 non-neoplastic lesions, were assessed retrospectively regarding their thin-section CT findings.

RESULTS

The frequency of wholly well-defined margin (p=0.001), spiculation (p=0.019), pleural indentation (p=0.016), air bronchograms (p=0.027), air-containing space (p=0.004) was significantly higher in neoplastic lesions than in non-neoplastic lesions. Thirty-four of 38 (89%) neoplastic lesions were well-defined in more than 50% of the circumference, of which nine had an air-containing space other than air bronchogram, whereas only one non-neoplastic lesion had these features.

CONCLUSION

A focal area of ground-glass opacity or ground-glass opacity predominance with a well-defined margin and air-containing space is more likely to be a neoplasm.

Multifocal Nodular Lymphoid Hyperplasia of the Lung

Nodular lymphoid hyperplasia (NLH) is one of the pulmonary lymphoproliferative disorders, and was initially described as pseudolymphoma. However, reports focusing on CT findings of NLH of the lung have been rare. We report a case of a pulmonary NLH in a 49-year-old woman who showed multiple pulmonary nodules on HRCT and was misdiagnosed preoperatively with adenocarcinoma on the basis of transthoracic cytology. A final diagnosis of NLH was made on postoperative histologic examination.

Lung Nodule Detection and Characterization With Multi-Slice CT

The influence of MSCT on nodule detection and characterization will be discussed. The objective is to improve understanding of the clinical issues involved in nodule detection, characterization, and management in light of technological advances. Topics to be covered are noninvasive characterization techniques, such as morphologic and density inspection on CT, nodule enhancement techniques, CT-PET, temporal nodule size assessment, and computer aided diagnosis for both detection and characterization.

CT Screening for Lung Cancer: Past and Ongoing Studies

It has been widely recognized that the oft-quoted randomized clinical trials (RCTs) of lung cancer screening by chest radiography--studies that were interpreted as showing no benefit--were seriously flawed. We begin by describing the shortcomings of these trials and presenting an analysis of the problems typically encountered in performing RCTs in this area. Screening for lung cancer using computed tomography (CT) has shown that CT offers great superiority over chest radiography in diagnosing small lung cancers in the three studies that performed both CT and chest radiography on all patients. The Early Lung Cancer Action Project (ELCAP), showed that false-positive results can be kept reasonably low and are much less common on repeat screening, and that CT screening can be managed with no notable excess of percutaneous or surgical biopsies when following a well-defined regimen of screening. This regimen details the parameters of the initial CT, the definition of a positive result, and the subsequent work-up of positive results. Following the updated International (I)-ELCAP protocol, it has been further found that (1) the frequency of positive results is low: 15% for the baseline cycle of screening and 6% for the subsequent cycles. (2) The frequency of screen-diagnoses as compared with all diagnoses is 97% or higher. (3) The relative frequency of presurgical Stage I is well over 80%; the median diameter of the screen-diagnosed cases on repeat screening is 8 mm (versus 15 mm at baseline screening). (4) A high percentage of the screen-diagnosed cases were genuine cancers which led to death if not treated. (5) The estimated 8-year cure rate for resected baseline screen-diagnosed lung cancers without evidence of lymph node metastases is 95% and for resected annual repeat cancers is 98%. (6) CT screening appears to be highly cost-effective. These preliminary results of CT screening suggests that the cure rate of screen-diagnosed lung cancer, using the I-ELCAP regimen of screening, may be over 70% as compared with that of usual care of 10% and that of chest radiographic screening of 20%.

Evolving Concepts in the Pathology and Computed Tomography Imaging of Lung Adenocarcinoma and Bronchioloalveolar Carcinoma

Purpose

To review recent advances in pathology and computed tomography (CT) of lung adenocarcinoma and bronchioloalveolar carcinoma (BAC).

Methods

A pathology/CT review panel of pathologists and radiologists met during a November 2004 International Association for the Study of Lung Cancer/American Society of Clinical Oncology consensus workshop in New York. The purpose was to determine if existing data was sufficient to propose modification of criteria for adenocarcinoma and BAC as newly published in the 2004 WHO Classification of Lung Tumors, and to address the pathologic/radiologic concept of diffuse/multicentric BAC.

Results

Solitary small, peripheral BACs have an excellent prognosis. Most lung adenocarcinomas with a BAC pattern are not pure BAC, but rather adenocarcinoma, mixed subtype with invasive patterns. This applies to tumors presenting with a diffuse/multinodular as well as solitary nodule pattern. The percent of BAC versus invasive components in lung adenocarcinomas appears to be prognostically important. However, a consensus definition of “minimally invasive” BAC with a favorable prognosis could not be achieved. While recognition of a BAC component is possible, the diagnosis of BAC with exclusion of invasive adenocarcinoma cannot be made by small biopsy or cytology specimens.

Conclusion

There is a need to work toward a mutual understanding and consensus between pathologists, clinicians, and researchers with the use of the term BAC versus adenocarcinoma. Future studies should make some attempt to quantitate these components and/or other features such as size of scar, size of invasive component, or pattern of invasion. Hopefully, this work will allow definition of a category of adenocarcinoma, mixed subtype with predominant BAC/minimal invasion and a favorable prognosis.

Adenosquamous carcinoma of the lung: CT—pathological correlation

AIM

To correlate CT morphological features and histopathological findings of adenosquamous carcinoma of the lung.

MATERIALS AND METHODS

In all, 29 patients underwent contrast-enhanced CT of an adenosquamous carcinoma of the lung, followed by resection of the cancer. Correlations between CT morphological and histopathological features were evaluated, including location, characteristics of margins, attenuation and the presence of necrosis.

RESULTS

The tumour was peripheral in 21 (72%) and central in 8 (28%) cases. The tumours varied in size from 1.1cm to 11.0cm (mean 3.8cm); 20 (69%) appeared as heterogeneous masses and 9 (31%) as homogeneous masses. The most common CT features were lobulation in 27 (93%), pleural tail in 22 (76%), spiculation in 17 (59%), necrosis in 15 (52%) and vessel convergence in 13 (45%). Among the 21 peripheral tumours, 14 (67%) showed intratumoural necrosis and 17 (81%) were heterogeneous. Among the 8 central tumours, only 1 (12.5%) showed intratumoural necrosis and 5 (62.5%) were homogeneous. These CT features corresponded mainly to solid tumour growth, which was composed of both squamous cell carcinomatous and adenocarcinomatous tissue.

CONCLUSION

Adenosquamous carcinoma of the lung is shown to be characteristically a solid, lobulated nodule or mass, more commonly peripheral than central. After intravenous injection of positive contrast medium, CT shows that the peripheral lesions are usually of heterogeneous soft-tissue attenuation.

Computer-aided diagnosis in chest radiology

Chest radiography is still a useful examination in various situations, although CT has become a modality of choice as a diagnostic examination in many cases. Current computer-aided diagnosis (CAD) schemes for chest radiographs include nodule detection, interstitial disease detection, temporal subtraction, differential diagnosis of interstitial disease, and distinction between benign and malignant pulmonary nodules. All of these schemes are demonstrated as providing potentially useful tools for radiologists when the output of these schemes is used as a "second opinion." There are some commercially available products for these schemes and more are expected to be available in the near future. The current status of CAD for CT is also discussed briefly in this article.

Loss of expression of E-cadherin and beta-catenin is associated with progression of pulmonary adenocarcinoma

The aim of the present study was to determine the association of loss of membranous expression of epithelial (E)-cadherin and beta-catenin with the progression of pulmonary adenocarcinoma. The expression of E-cadherin and beta-catenin was examined in 154 cases of pulmonary adenocarcinoma, including 49 cases of atypical adenomatous hyperplasia (AAH), 40 cases of bronchioloalveolar carcinoma (BAC), 42 cases of BAC-dominant type of adenocarcinoma with mixed subtypes (early MX) and 23 cases of BAC-recessive type of adenocarcinoma with mixed subtypes (overt MX), by immunohistochemistry. E-cadherin expression was positive in all cases of AAH, in 37 cases (92.5%) of BAC and in 34 cases (81.0%) of early MX, while it was positive in three cases (13.0%) of overt MX. beta-Catenin expression was positive in 47 cases (95.9%) of AAH, in 28 cases (70%) of BAC, in 32 cases (76.2%) of early MX and in 11 cases (47.8%) of overt MX. The rates of expression of E-cadherin and beta-catenin among cases of AAH, BAC, early MX and overt MX were significantly reduced. Loss of expression of E-cadherin and beta-catenin may play an important role in the progression of pulmonary adenocarcinoma, and these events occur before structural destruction of the alveolar wall by invasion of carcinoma cell.

Malignant versus Benign Nodules at CT Screening for Lung Cancer: Comparison of Thin-Section CT Findings

PURPOSE

To evaluate thin-section computed tomographic (CT) characteristics of malignant nodules on the basis of overall appearance (pure ground-glass opacity [GGO], mixed GGO, or solid opacity) in comparison with the appearance of benign nodules.

MATERIALS AND METHODS

Institutional review board approval and patient consent were obtained. Follow-up diagnostic CT was performed in 747 suspicious pulmonary nodules detected at low-dose CT screening (17 892 examinations). Of 747 nodules, 222 were evaluated at thin-section CT (1-mm collimation), which included 59 cancers and 163 benign nodules (3-20 mm). Thin-section CT findings of malignant versus benign nodules with pure GGO (17 vs 12 lesions), mixed GGO (27 vs 29 lesions), or solid opacity (15 vs 122 lesions) were analyzed. Fisher exact test for independence was used to compare differences in shape, margin, and internal features between benign and malignant nodules. Positive predictive value (PPV) was analyzed when a category was significantly different from the others.

RESULTS

Among nodules with pure GGO, a round shape was found more frequently in malignant lesions (11 of 17, 65%) than in benign lesions (two of 12, 17%; P = .02; PPV, 85%); mixed GGO, a subtype with GGO in the periphery and a high-attenuation zone in the center, was seen much more often in malignant lesions (11 of 27, 41%) than in benign lesions (two of 29, 7%; P = .004; PPV, 85%). Among solid nodules, a polygonal shape or a smooth or somewhat smooth margin was present less frequently in malignant than in benign lesions (polygonal shape: 7% vs 38%, P = .02; smooth or somewhat smooth margin: 0% vs 63%, P < .001), and 98% (46 of 47) of polygonal nodules and 100% (77 of 77) of nodules with a smooth or somewhat smooth margin were benign.

CONCLUSION

Recognition of certain characteristics at thin-section CT can be helpful in differentiating small malignant nodules from benign nodules.

Radiologists' performance for differentiating benign from malignant lung nodules on high-resolution CT using computer-estimated likelihood of malignancy

OBJECTIVE

The purpose of our study was to evaluate whether a computer-aided diagnosis (CAD) scheme can assist radiologists in distinguishing small benign from malignant lung nodules on high-resolution CT (HRCT).

MATERIALS AND METHODS

We developed an automated computerized scheme for determining the likelihood of malignancy of lung nodules on multiple HRCT slices; the likelihood estimate was obtained from various objective features of the nodules using linear discriminant analysis. The data set used in this observer study consisted of 28 primary lung cancers (6-20 mm) and 28 benign nodules. Cancer cases included nodules with pure ground-glass opacity, mixed ground-glass opacity, and solid opacity. Benign nodules were selected by matching their size and pattern to the malignant nodules. Consecutive region-of-interest images for each nodule on HRCT were displayed for interpretation in stacked mode on a cathode ray tube monitor. The images were presented to 16 radiologists-first without and then with the computer output-who were asked to indicate their confidence level regarding the malignancy of a nodule. Performance was evaluated by receiver operating characteristic (ROC) analysis.

RESULTS

The area under the ROC curve (Az value) of the CAD scheme alone was 0.831 for distinguishing benign from malignant nodules. The average Az value for radiologists was improved with the aid of the CAD scheme from 0.785 to 0.853 by a statistically significant level (p = 0.016). The radiologists' diagnostic performance with the CAD scheme was more accurate than that of the CAD scheme alone (p < 0.05) and also that of radiologists alone.

CONCLUSION

CAD has the potential to improve radiologists' diagnostic accuracy in distinguishing small benign nodules from malignant ones on HRCT.

Solitary pulmonary nodules

The purpose of this study was to determine an optimal slice thickness that was efficient in differentiating malignant from benign solitary pulmonary nodules (SPNs) on high-resolution computed tomography (HRCT) images. For a total of 92 SPNs, four radiologist indicated their confidence level for the malignant or benign SPN on the CT images presented in 1-, 3-, and 5-mm slice thickness. HRCT could be used to differentiate more accurately the malignant nodules from the benign ones using 1-mm-thick sections than 3- or 5-mm-thick sections.

Population screening for lung cancer

The feasibility of diagnosing small stage 1 lung cancers using low-dose chest computed tomography in asymptomatic at-risk individuals has been demonstrated in multiple studies. However, it has yet to be proved that the introduction of a chest computed tomography screening programme would do more good than harm at an acceptable cost.

Small lung tumors with the size of 1cm or less in diameter: clinical, radiological, and histopathological characteristics

BACKGROUND

The detection rate of small nodules in the peripheral lung area is increasing due to the widespread use of CT scanning. However, the radiological and pathological characteristics of very small tumors have not been fully investigated.

METHODS

We evaluated 44 lung tumors with the size of 1cm or less in diameter resected from 38 patients (19 men and 19 women, with an average of 62 years) from 1997 through 2001. The clinical records, the findings of high-resolution CT (HRCT) and histopathological features of resected specimens were analyzed. Adenocarcinoma was histologically further subclassified into types A to F according to the Noguchi's classification.

RESULTS

Lobectomy was performed in 20 patients, wedge resection in 15 and segmentectomy in 3, respectively. Thirty-two tumors were adenocarcinomas, 4 were squamous cell carcinomas, and eight were atypical adenomatous hyperplasia (AAH), respectively. All carcinoma cases were proved to be stage IA. In adenocarcinoma, type A was detected in 12 tumors, type B in 13, type C in 1, type D in 2, type E in 1, and type F in 3, respectively. Most of AAH and type A showed pure ground-glass attenuation on HRCT scan, whereas types B to F as well as squamous cell carcinoma frequently had malignant CT signs such as lobulation and convergence of peripheral vessels. Lymphatic or vascular invasion was observed in two adenocarcinomas (types D and F) and two squamous cell carcinomas, and HRCT scan of these four tumors showed soft-tissue attenuation occupying more than two-thirds of each nodule. All patients are currently alive without signs of recurrence after a mean follow-up period of 35.5 months.

CONCLUSION

Types A and B of adenocarcinoma were the most common histologic types among lung tumors with the size of 1cm or less in diameter. Limited lung resection appears to be an adequate for such small lung tumors in which soft-tissue attenuation consists of less than two-thirds of the nodule on HRCT.

Progression of focal pure ground-glass opacity detected by low-dose helical computed tomography screening for lung cancer

OBJECTIVE

To clarify the progression of focal pure ground-glass opacity (pGGO) detected by low-dose helical computed tomography (CT) screening for lung cancer.

METHODS

A total of 15,938 low-dose helical CT examinations were performed in 2052 participants in the screening project, and 1566 of them were judged to have yielded abnormal findings requiring further examination. Patients with peripheral nodules exhibiting pGGO at the time of the first thin-section CT examination and confirmed histologically by thin-section CT after follow-up of more than 6 months were enrolled in the current study. Progression was classified based on the follow-up thin-section CT findings.

RESULTS

The progression of the 8 cases was classified into 3 types: increasing size (n = 5: bronchioloalveolar carcinoma [BAC]), decreasing size and the appearance of a solid component (n = 2: BAC, n = 1; adenocarcinoma with mixed subtype [Ad], n = 1), and stable size and increasing density (n = 1: BAC). In addition, the decreasing size group was further divided into 2 subtypes: a rapid-decreasing type (Ad: n = 1) and a slow-decreasing type (BAC: n = 1). The mean period between the first thin-section CT and surgery was 18 months (range: 7-38 months). All but one of the follow-up cases of lung cancer were noninvasive whereas the remaining GGO with a solid component was minimally invasive.

CONCLUSIONS

The pGGOs of lung cancer nodules do not only increase in size or density, but may also decrease rapidly or slowly with the appearance of solid components. Close follow-up until the appearance of a solid component may be a valid option for the management of pGGO.

The pitfalls of lung cancer screening

Lung cancer screening has received extensive attention for a number of years. As yet the goal of such a screening programme, a reduction in lung cancer mortality proven by a large randomised controlled trial, has not been achieved. Instead we are left with a number of unanswered questions and practical problems. In addition to the basic requirements for an effective screening programme, this review will identify the main pitfalls in lung cancer screening, with particular reference to multislice computed tomography. The specific difficulties relating to the identification of unimportant disease, the failure to identify important disease successfully, the consequences of investigating and treating identified disease and the financial costs will all be discussed.

Consistency of reporting basic characteristics of lung nodules and masses on computed tomography1

RATIONALE AND OBJECTIVES

To assess the consistency of chest computed tomography (CT) reports in describing basic characteristics of lung nodules and masses.

MATERIALS AND METHODS

We retrospectively identified 107 consecutive patients with preoperative chest CT scans before resection of a lung nodule or mass over a 4-year period within a single institution. There were 54 men and 53 women with a mean age of 64 years (range, 37-86) years. The CT scans were reported by a cohort of 20 board-certified radiologists, three of whom reviewed more than 10 CT scans (n = 60 exams). The CT reports were reviewed for lesion characteristics including size, location, and description of margins, presence or absence of calcification, fat and cavitation, and the diagnosis or differential diagnosis. Pathology reports were reviewed for the same characteristics and the final diagnosis. Both CT and pathologic reports of emphysema were noted in lobectomy specimens. The differences between the interpreting radiologists were also sought.

RESULTS

A diagnosis or differential diagnosis was provided in 90% (96/107) of CT reports. The diagnosis of bronchogenic carcinoma was made in 78% (59/76) of those with bronchogenic carcinoma, compared with 65% (20/31) of those with other diagnoses (P = NS). Radiologists described the margins of the nodule or mass in 64% (68/107) of cases, similar in frequency to 66% of pathologists (71/107). Radiologic description of an irregular/spiculated margins predicted bronchogenic carcinoma in 86% of cases (42/49), while a smooth/lobulated margins predicted a diagnosis other than bronchogenic carcinoma in 58% (11/19; P < .05). The presence or absence of calcification was noted in 7% (5/76) of cases of bronchogenic carcinoma and 32% (10/31) of those with other diagnoses (P < .05, chi square). Both radiologists and pathologists consistently reported the size of the lesions with a correlation coefficient between radiology and pathology reports of 0.88. CT reporting of the characteristics of the lesion did not differ among lesions of different sizes. There was no significant difference between major reporters (more than 10 cases) in this study. Emphysema in the surrounding lung was reported in 25% (20/81) of radiology and 38% (31/81) of pathology reports (P = NS).

CONCLUSION

This series demonstrates a lack of consistent reporting of the margins of resected lung nodules both on CT and on pathologic specimens. The presence or absence of calcification was inconsistently reported, although more frequently noted in diagnoses other than bronchogenic carcinoma. As large-scale CT screening for lung cancer becomes more common, radiologists should prioritize developing and adopting standardized reporting criteria for the CT evaluation of lung nodules.

A clinicopathological study of resected subcentimeter lung cancers: a favorable prognosis for ground glass opacity lesions

BACKGROUND

Owing to the advent of refined chest computed tomography (CT) images with higher resolution and CT screening programs, more faint and smaller lung cancers are being discovered. These include small-sized lung cancers such as those with a subcentimeter diameter, which had never been picked up on the routine chest roentgenogram films. However their clinicopathological characteristics with special reference to the proper surgical mode are not fully described so far.

METHODS

During a 10-year period from 1991 through 2000 a total of 1,769 lung tumors were resected at the National Cancer Center Hospital, Tokyo. According to the pathology files of these patients, 51 patients had a primary tumor with the diameter of 1 cm or less. Three tumors arising in the bronchial lumina of hilum with a squamous cell carcinoma histology were excluded and the remaining 48 tumors of peripheral origin were studied. The clinicopathological features were analyzed according to three types of appearance on high-resolution CT: non-solid ground glass opacity (GGO) type (n = 19); part-solid GGO type (n = 9); and solid type (n = 20). Non-solid GGO is made up of homogeneous moderate increased density on CT, which cannot obscure the bronchovascular structure, whereas partly solid GGO contains a mere solid part but did not exceed 50% of the whole area (n = 9). All other lesions were considered solid type.

RESULTS

For the three types of lesions, the distribution of age and sex was similar with the average age of 61 years and an almost even distribution of male/female patients. Although 6 patients had symptoms, the symptoms were not associated with the nodule itself. Twenty-six patients (54%) were screen-detected (16 chest roentgenogram films and 10 CT scans) and the others were detected by incidentally taken chest roentgenogram film or CT for other reasons than nodules detected. Two squamous carcinomas were positive for sputum cytology. Preoperative cytologic/histologic diagnosis was given in 14 patients (29%). The histologic type of GGO lesion was bronchioloalveolar carcinoma in all 28 cases. In solid lesions, besides 16 adenocarcinomas 2 cases of squamous cell carcinoma, 1 case each of small cell carcinoma and carcinoid tumor was seen. Lymph node involvement was seen only in 3 patients with solid lesions (N1 in 2 patients, N2 in 1 patient). As for operative mode, the limited resection was performed for 15 GGO lesions (54%) and 4 solid lesions (20%). Tumor recurrence was seen in 2 patients with solid lesions-1 in bone and the other in locoregional lymph node, and the former died of disease.

CONCLUSIONS

Among subcentimeter lung cancers, GGO lesions (both non-solid and part-solid) constitute true early lung cancers. Since they have minimal or no invasive growth, limited resection for cure is justified. Conversely the solid lesion had significant invasive features such as lymph node metastasis. Lobectomy should remain as the standard mode of surgery despite such small size.

Low-dose computed tomography screening for lung cancer in a general population

RATIONALE AND OBJECTIVES

To report the detection rate for lung cancers in computed tomography (CT) screening in Japanese adults, and to analyze differences in the appearance of the cancers in non-smokers versus smokers.

MATERIALS AND METHODS

Subjects consisted of 7,847 Japanese adults who received low-dose CT screening at least once in a 3-year period. The detection rate of lung cancers and the correlation of imaging, clinical, and pathologic findings of cancers in non-smokers versus smokers were examined.

RESULTS

The detection rate for lung cancer was 1.1% for both non-smokers (45 of 4,251) and smokers (39 of 3,596). The prevalence of well-differentiated adenocarcinomas was greater in non-smokers (88%; 22 of 25) than in smokers (29%; 4 of 14) (P < .001). The prevalence and incidence of pathologic stage IA disease were greater in non-smokers than in smokers (92%; [22 of 24] vs 58% [7 of 12], and 100% [19 of 19] vs 70% [14 of 20]) (both P < .05). The mean size of the tumors in the non-smokers (12.4 mm) was smaller than that in smokers (18.2 mm) (P < .001). The percentage of cancers categorized as pure or mixed ground-glass opacity (86%; 38 of 44) on CT was greater in non-smokers than in smokers (46%; 16 of 35) (P < .001).

CONCLUSION

Most of the lung cancers in non-smokers were slow-growing adenocarcinomas appearing as faint ground-glass opacities on CT, whereas rapidly growing cancers appearing as solid nodules were more commonly seen in smokers.

Indeterminate solitary pulmonary nodules revealed at population-based CT screening of the lung: using first follow-up diagnostic CT to differentiate benign and malignant lesions

OBJECTIVE

We studied the role of the first follow-up diagnostic CT for differentiating benign and malignant lesions in indeterminate solitary pulmonary nodules revealed at CT screening for lung cancer in which a total of 13,786 CT examinations (46% in women and 54% in men; 46% were smokers; mean age, 62 years) were performed.

MATERIALS AND METHODS

We reviewed thin-section CT findings on the initial diagnostic CT (lesion size; percentages of ground-glass-opacity areas of lesion; and presence or absence of lobulation, spiculation, air bronchogram, cavity, satellite lesions, pleural tag, concave margins, polygonal shape, and peripheral subpleural lesion) in 80 pulmonary nodules (36 malignancies and 44 benign lesions) of 80 patients. We evaluated changes in size (regression, no change, or growth) on the first follow-up CT performed 42-120 days (mean, 93 days) after the initial CT.

RESULTS

The greatest accuracy (81%) with 89% sensitivity and 75% specificity for determining malignancy was attained with a combined criterion of growth of lesions or predominantly ground-glass-opacity lesions. Of all criteria that were specific to malignancy, the greatest sensitivity (50%) was achieved with a combination of growth or no change in size of lesions and predominantly ground-glass opacity and no concave margins. Of all criteria that were specific to benign lesions, the greatest sensitivity (45%) was attained with a combination of lesion regression or polygonal shape.

CONCLUSION

Follow-up CT findings were useful, and a combination of findings on initial CT and follow-up CT was optimal for differentiating benign and malignant pulmonary nodules.

Small solitary pulmonary nodules (< or =1 cm) detected at population-based CT screening for lung cancer: Reliable high-resolution CT features of benign lesions

OBJECTIVE

We assessed thin-section CT features specific to benignity in solitary pulmonary nodules of 1 cm or smaller that were detected at population-based CT screening for lung cancer.

MATERIALS AND METHODS

Two reviewers independently made qualitative (presence or absence of lobulation, spiculation, air bronchogram, cavity, satellite lesions, pleural tag, concave margins, polygonal shape, and peripheral subpleural lesion) and quantitative (lesion size, percentage of ground-glass opacity areas, and two- and three-dimensional ratios of lesion) assessments in CT images of 72 nodules (25 lung cancers, seven atypical adenomatous hyperplasias, and 40 benign lesions). Optimal criteria specific to benignity were studied.

RESULTS

The prevalence of polygonal shape (p = 0.005 and p = 0.019, reviewer 1 and reviewer 2), peripheral subpleural lesion (p = 0.011 and p = 0.033), a predominantly solid lesion (p < 0.001 and p < 0.001), and three-dimensional ratios (p < 0.001 and p < 0.001) were greater in benign lesions than in malignancies. The prevalence of a predominantly solid lesion (p < 0.001 and p < 0.001) was greater in benign lesions than in atypical adenomatous hyperplasias, and the prevalence of a peripheral subpleural lesion (p = 0.004 and p = 0.012) was greater in atypical adenomatous hyperplasias than in malignancies. Using a single CT feature, polygonal shape and a three-dimensional ratio of greater than 1.78 showed 100% specificity for both reviewers. Among all combinations of CT findings specific to benignity, a combined criterion of a predominantly solid lesion and peripheral subpleural lesion or polygonal shape or the three-dimensional ratio attained the highest sensitivity (63% and 60%) for both reviewers.

CONCLUSION

A combined criterion of CT features was optimal for predicting benign pulmonary lesions.

CT findings and progression of small peripheral lung neoplasms having a replacement growth pattern

OBJECTIVE

We investigated the imaging findings and progression of replacement lung neoplasms that were revealed on thin-section CT and serial CT.

MATERIALS AND METHODS

We evaluated the age of patients and thin-section CT findings (lesion size; percentage of ground-glass opacity areas; and presence or absence of solid portions, lobulation, coarse spiculation, air bronchogram, cavity, multiplicity, and pleural tags) in 73 lesions (11 atypical adenomatous hyperplasias, 17 type A [Noguchi's classification], 18 type B, and 27 type C small peripheral adenocarcinomas). We compared the serial findings of 48 of 73 lesions on low-dose screening CT (n = 21) or thin-section CT (n = 27) obtained at a mean interval of 450 days (range, 85-951 days). Progression from atypical adenomatous hyperplasia through type A to type B and then to type C tumor was studied using trend tests.

RESULTS

A significant linear trend was seen for lesion size (r = 0.55; p < 0.001), percentages of ground-glass opacity areas (r = 0.75; p < 0.001), and the prevalence of lobulation (p < 0.001), spiculation (p = 0.001), air bronchogram (p = 0.023), cavity (p = 0.046), pleural tag (p < 0.001), and solid portions (p < 0.001). In general from serial CT assessment, lesions were recognized first as a ground-glass opacity nodule (56% of 48 lesions) with subsequent increase in size (75%), then solid portions appeared in the nodule (17%), and finally solid portions increased (23%) with occasional augmentation of tissue contraction (6%).

CONCLUSIONS

CT analysis revealed stepwise progression of replacement-type lung neoplasms.

Measurement of localized ground-glass attenuation on thin-section computed tomography images: correlation with the progression of bronchioloalveolar carcinoma of the lung

RATIONALE AND OBJECTIVE

This study was to measure localized ground-glass attenuation (GGA) in the peripheral lung on thin-section computed tomography (CT) and to assess any relationship between the attenuation and lesion.

MATERIALS AND METHODS

Twenty-eight surgically resected tumors with localized GGA at thin-section CT were studied. The tumors were histologically diagnosed as 8 atypical adenomatous hyperplasia (AAH), 11 bronchioloalveolar carcinoma (BAC), and 9 BAC with fibrosis. We assumed three concentric circles, which were 0.8, 1.0, and 1.2 times the diameter of each tumor and measured the average CT values corresponding to inside each circle. We calculated a difference in CT value between 0.8 and 1.2 times the diameter of the tumor and defined as the contrast index.

RESULTS

The contrast index for tumors with AAH, BAC, and BAC with fibrosis were 19.8 +/- 8.3, 42.5 +/- 16.0 (P < 0.05 vs. group with AAH), and 111.4 +/- 32.6 (P < 0.0001 vs. Group with BAC), respectively. The contrast index became greater in the stepwise progression from AAH to BAC and from BAC to BAC with fibrosis.

CONCLUSION

The contrast index correlated histologic findings of the tumor growth in BAC. The contrast index may be a useful and objective measurement for determining surgical treatment for localized GGA in preoperative diagnosis.

Lung cancers missed at low-dose helical CT screening in a general population: comparison of clinical, histopathologic, and imaging findings

PURPOSE

To compare clinical, histopathologic, and imaging features of lung cancers missed at low-radiation-dose helical computed tomography (CT).

MATERIALS AND METHODS

Eighty-three primary lung cancers were found during an annual low-dose CT screening program and confirmed histopathologically at either surgery or biopsy. Thirty-two of these lung cancers were missed on 39 CT scans: on 23 scans owing to detection errors and on 16 owing to interpretation errors. The clinical characteristics, CT features, and histopathologic findings of these missed lung cancers were correlated.

RESULTS

All missed cancers were intrapulmonary, and 28 (88%) were stage IA. All 20 detection errors occurred in cases of adenocarcinoma, 17 (85%) of which were well-differentiated tumors and 11 (55%) of which were in nonsmoking women. The mean size of cancers missed owing to detection error, 9.8 mm, was smaller than that of cancers missed owing to interpretation error, 15.9 mm (P <.001). In the detection error group, the percentages of nodules with ground-glass opacity (91%) or judged to be subtle (91%) were greater than those of nodules in the interpretation error group (38% and 25%, respectively) (P <.001). In the detection error group, 83% (19/23) of cancers were overlapped with, obscured by, or similar in appearance to normal structures such as pulmonary vessels. On 14 of the 16 CT scans with which there were interpretation errors, the CT findings mimicked benign disease, and the patients also had underlying lung disease, such as tuberculosis, emphysema, or lung fibrosis.

CONCLUSION

The lung cancers missed at low-dose CT screening in this series generally were very subtle and appeared as small faint nodules, overlapping normal structures, or opacities in a complex background of other disease.

Randomized controlled trial with low-dose spiral CT for lung cancer screening: feasibility study and preliminary results

PURPOSE

To assess the feasibility of conducting a randomized controlled trial for lung cancer screening.

MATERIALS AND METHODS

Subjects are being recruited into a randomized controlled trial to undergo either low-dose spiral computed tomography (CT) or observation. Subjects are from a high-risk group with known chronic obstructive pulmonary disease and sputum atypia and a moderate-risk group randomly selected from the general population of a Veterans Affairs Medical Center. All subjects must be 50-80 years of age with 30 or more pack-years of cigarette smoking and must not have undergone chest CT during the previous 3 years. Baseline screening CT is performed with 50 mA, 120 kVp, 5-mm collimation, and a pitch of 2. CT scan interpretation and management of nodules is based on Society of Thoracic Radiology guidelines. The chi(2) test for categoric data was used for statistical analysis.

RESULTS

To date, 304 eligible subjects have been contacted, and 239 (79%) have agreed to participate in the trial. One hundred nineteen (88%) of the 136 subjects in the high-risk group and 120 (71%) of the 168 subjects in the moderate-risk group agreed to randomization (P <.001). To date, 190 subjects have been randomized. Of the first 92 subjects examined with CT, 22 (40%) of 55 in the high-risk group and eight (22%) of 37 in the moderate-risk group had one to six noncalcified nodules that required follow-up (P =.07). In all but three subjects, nodules were smaller than 5 mm. Two of the three larger nodules were malignancies.

CONCLUSION

Findings of this study indicate that a randomized controlled trial of CT to screen for lung cancer is feasible.

Innovative molecular and imaging approaches for the detection of lung cancer and its precursor lesions

Current approaches for the therapy of lung cancer, the majority of which being advanced cancers, have failed to impact on long term survival. The key to improvement lies in the combination of early diagnosis and the introduction of novel targeted therapies. In this article we review some of the innovative approaches, both imaging and molecular, that are currently under investigation for early detection. Because lung cancers may arise in the central or peripheral compartments of the lung, newer approaches must target tumours arising in both of these compartments. Specimens available for analysis include sputa and blood. Detection of genetic changes in peripheral blood is a promising avenue being explored by several groups. Molecular techniques discussed include gene mutations, detection of nuclear riboprotein, methylation related silencing of genes and malignancy associated changes. Newer imaging technologies include autofluorescence bronchoscopy, virtual bronchoscopy, optical coherent tomography and confocal microscopy. Although the impact of these new technologies on survival has not been determined, they offer a wide range of exciting new approaches. In time they may completely revamp the present highly conservative and unsuccessful approaches to early diagnosis.