Localized pure ground-glass opacity on high-resolution CT: histologic characteristics

PURPOSE: The aim of this study is to assess the histologic characteristics in cases of localized pure ground-glass opacity (LPGGO) that do not exhibit consolidation on high-resolution CT (HRCT) images. METHOD: Twenty surgically resected lesions from 20 consecutive cases were retrospectively investigated. Each of the 20 lesions had exhibited LPGGO on HRCT images. The HRCT images and histopathologic findings were examined for correlations. RESULTS: The areas of LPGGO had a maximum diameter of 2.0-24 mm on the HRCT images. Histopathology of the LPGGO lesions resulted in diagnosis of fibrosis (n = 3; 15%), atypical adenomatous hyperplasia (n = 5; 25%), bronchioloalveolar carcinoma (n = 10; 50%), and adenocarcinoma with stromal invasion (n = 2; 10%). Nonaerogenous components corresponding to solid components without normal alveolar septal destruction were pathologically observed in 15 of the 20 lesions. The diameter of the nonaerogenous components varied between 0.2 and 2.0 mm. CONCLUSION: Because 10% of LPGGO lesions include invasive disease, patients with LPGGO should undergo pathologic examination for confirmation.     

A case of adenocarcinoma with mixed subtypes displaying ground-glass opacity on high-resolution CT

We report a case of adenocarcinoma with mixed subtypes with pleural dissemination and lymphatic permeation, although the CT results showed ground-glass opacity that led to the diagnosis of bronchioloalveolar carcinoma without foci of active fibroblastic proliferation.     

容积数据高分辨力CT重建诊断肺部磨玻璃密度影

目的：探讨容积数据高分辨力CT重建（VHRCT）对肺部磨玻璃密度影的临床诊断价值。方法：对27例肺部弥漫性磨玻璃密度灶和5例局限性磨玻璃密度灶患者进行MSCT和HRCT扫描及VHRCT图像重建,对HRCT及VHRCT图像质量进行分级评分（3级评分法）。结果：27例肺部弥漫性磨玻璃密度灶患者的VHRCT和HRCT图像评分结果分别是52分和49分,2种图像质量的差异无统计学意义（Z=-1.00,P=0.317）;5例局限性磨玻璃密度患者的VHRCT和HRCT图像评分结果分别1分和0分,2种图像质量的差异无统计学意义（Z=-1.00,P=0.317）。结论：VHRCT重建图像评价肺部磨玻璃密度影的价值与HRCT扫描图像相当,VHRCT重建图像为观察肺部磨玻璃密度影提供了一种简单易行的方法。     

Quantification of ground-glass opacity on high-resolution CT of small peripheral adenocarcinoma of the lung: pathologic and prognostic implications.

OBJECTIVE: The purpose of our study was to correlate the high-resolution CT findings of small peripheral adenocarcinoma of the lung with underlying histopathology and to evaluate the prognostic implications of the CT findings. MATERIALS AND METHODS: The high-resolution CT findings of small peripheral adenocarcinoma of the lung in 224 patients were analyzed by two independent observers for location, size, marginal characteristics, and extent of ground-glass opacity and necrosis. The pathologic specimens were reviewed by an experienced lung pathologist. RESULTS: One hundred and thirty-two patients had bronchioloalveolar carcinoma and 92 had adenocarcinoma. The extent of ground-glass opacity was greater in bronchioloalveolar carcinomas (mean +/- SD, 29% +/- 31.6%) than in other adenocarcinomas (8% +/- 13.3%) (p < 0.001). The extent of ground-glass opacity was significantly greater in patients without recurrence (p = 0.020) and those without nodal (p = 0.017) or distant (p = 0.007) metastases than in patients with nodal or distant metastases or in whom the carcinoma had recurred. CONCLUSION: The extent of ground-glass opacity in a nodule is greater in bronchioloalveolar carcinomas than in other adenocarcinomas. Greater extent of ground-glass opacity also correlates with improved prognosis.     

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.     

Computer-aided diagnosis of localized ground-glass opacity in the lung at CT: initial experience

The purpose of this study was to develop an automated scheme to facilitate detection of localized ground-glass opacity (GGO) in the lung at computed tomography (CT). Institutional review board approval and informed consent were not required. Two radiologists reviewed CT images from 14 patients (five men, nine women) who had lung cancer or metastasis and whose malignancy was classified as GGO. The lung region was sampled and completely covered with contiguous, 50% overlapping regions of interest (ROIs) measuring 30 x 30 pixels in size. The lung area within each ROI was analyzed to compute texture features and gaussian curve fitting features. Performance of the artificial neural networks (ANNs) measured by using the area under the receiver operating characteristic curve was 0.92. With a threshold of 0.9, the sensitivity of the ANN for detecting GGO ROIs was 94.3% (280 of 297 ROIs), and the positive predictive value was 29.1% (280 of 963 ROIs). A computerized scheme may hold promise in facilitating detection of localized GGO at CT.     

毛玻璃样密度肺结节的CT诊断和鉴别诊断

由于CT的普及、高分辨力CT的广泛应用以及利用CT进行早期肺癌的筛查,使隐蔽的结节状毛玻璃样密度(nodular ground-glass opacity, NGGO)和局灶性毛玻璃样密度(focal ground-glass opacity, FGGO)影的发现率逐渐升高,有关其定性诊断问题也日益引起外科和放射科医师的关注.     

毛玻璃样密度肺结节的CT诊断和鉴别诊断

由于CT的普及、高分辨力CT的广泛应用以及利用CT进行早期肺癌的筛查,使隐蔽的结节状毛玻璃样密度(nodular ground-glass opacity,NGGO)和局灶性毛玻璃样密度(focal ground-glass opacity,FGGO)影的发现率逐渐升高,有关其定性诊断问题也日益引起外科和放射科医师的关注。本文就毛玻璃样密度肺结节的定义、病理基础、CT检查的技术要求以及CT诊断和鉴别诊断征象予以介绍。     

Computer-aided diagnosis of lung cancer: definition and detection of ground-glass opacity type of nodules by high-resolution computed tomography

Purpose  The ground-glass opacity (GGO) of lung cancer is identified only subjectively on computed tomography (CT) images as no quantitative characteristic has been defined for GGOs. We sought to define GGOs quantitatively and to differentiate between GGOs and solid-type lung cancers semiautomatically with a computer-aided diagnosis (CAD). Methods and materials  High-resolution CT images of 100 pulmonary nodules (all peripheral lung cancers) were collected from our clinical records. Two radiologists traced the contours of nodules and distinguished GGOs from solid areas. The CT attenuation value of each area was measured. Differentiation between cancer types was assessed by a receiver-operating characteristic (ROC) analysis. Results  The mean CT attenuation of the GGO areas was −618.4 ± 212.2 HU, whereas that of solid areas was −68.1 ± 230.3 HU. CAD differentiated between solidand GGO-type lung cancers with a sensitivity of 86.0% and specificity of 96.5% when the threshold value was −370 HU. Four nodules of mixed GGOs were incorrectly classified as the solid type. CAD detected 96.3% of GGO areas when the threshold between GGO and solid areas was 194 HU. Conclusion  Objective definition of GGO area by CT attenuation is feasible. This method is useful for semiautomatic differentiation between GGOs and solid types of lung cancer.     

肺部局灶性磨玻璃密度结节MSCT诊断

目的 分析肺部局灶磨玻璃密度结节( focal ground-glass opacity,fGGO)的多层螺旋CT(MSCT)表现,以寻找对fGGO良恶性鉴别诊断有价值的影像学征象.方法 分析34例(40个)经病理或抗炎治疗后证实的fGGO患者的基本临床资料、病灶大小、部位、类型及MSCT表现,用Fisher确切概率法对比分析fGGO中细支气管肺泡癌(BAC)、非典型性腺瘤样增生(AAH)及良性三者MSCT表现之间是否存在差异,P<0.05为差异具有统计学意义.结果 40个fGGO中,混合性GGO(mGGO) 19个,单纯性GGO(pGGO)21个;BAC 27个,AAH 8个,良性5个.患者的性别、病灶形状在良恶性fGGO之间差异均无统计学意 义(P>0.05).mGGO与pGGO的良恶性发病率差异有统计学意义(χ2=10.506,P=0.003),17个mGGO为恶性结节.发病年龄、病灶大小、部位、边缘形态(分叶、毛刺、光整)、界面(清楚、模糊)、内部结构(细支气管征)、邻近结构(胸膜凹陷征)在BAC、AAH及良性病变之间差异均有统计学意义(P<0.05).结论 fGGO病灶边缘分叶、清楚的界面、细支气管征、胸膜凹陷征为MSCT诊断恶性fGGO的重要征象.     

Persistent pulmonary nodular ground-glass opacity at thin-section CT: histopathologic comparisons

PURPOSE: To retrospectively compare pure pulmonary ground-glass opacity (GGO) nodules observed on thin-section computed tomography (CT) images with histopathologic findings. MATERIALS AND METHODS: The institutional review board approved this study and waived informed consent. Histopathologic specimens were obtained from 53 GGO nodules in 49 patients. CT scans were assessed in terms of nodule size, shape, contour, internal characteristics, and the presence of a pleural tag. The findings obtained were compared with histopathologic results. Differences in thin-section CT findings according to histopathologic diagnoses were analyzed by using the Kruskal-Wallis test or Fisher exact test. RESULTS: Of 53 nodules in 49 patients (20 men, 29 women; mean age, 54 years; range, 29-78 years), 40 (75%) proved to be broncholoalveolar cell carcinoma (BAC) (n=36) or adenocarcinoma with predominant BAC component (n=4), three (6%) atypical adenomatous hyperplasia, and 10 (19%) nonspecific fibrosis or organizing pneumonia. No significant differences in morphologic findings on thin-section CT scans were found among the three diseases (all P>0.05). A polygonal shape (25%, 10 of 40 nodules) and a lobulated or spiculated margin (45%, 18 of 40) in BAC or adenocarcinoma with predominant BAC component were caused by interstitial fibrosis or infiltrative tumor growth. A polygonal shape and a lobulated or spiculated margin were observed in two (20%) and three (30%) of 10 nodules, respectively, in organizing pneumonia/fibrosis were caused by granulation tissue aligned in a linear manner in perilobular regions with or without interlobular septal thickening. CONCLUSION: About 75% of persistent pulmonary GGO nodules are attributed to BAC or adenocarcinoma with predominant BAC component, and at thin-section CT, these nodules do not manifest morphologic features that distinguish them from other GGO nodules with different histopathologic diagnoses.     

Identification and characterization of focal ground-glass opacity in the lungs by high-resolution CT using thin-section multidetector helical CT: experimental study using a chest CT phantom

Purpose The aim of this study was to investigate how much the radiation dose can be reduced for the identification and characterization of focal ground-glass opacities (GGOs) by high resolution computed tomography (HRCT). Materials and methods A chest CT phantom including GGO nodules was scanned with a 40-detector CT scanner. The scanning parameters were as follows: tube voltage 120 kVp; beam collimation 32 × 1.25 mm; thickness and intervals 1.25 mm; tube current and rotation time 180, 150, 120, 90, 60, and 30 mA. 180 mA was the standard. Using a three-point scale at different currents, we visually evaluated image quality. Furthermore, we carried out observer performance tests using receiver operating characteristic (ROC) analysis to evaluate the ability to identify GGO nodules at each current. Results By visual analysis, the scores for all particulars were significantly lower on images obtained at less than 120 mA than at 180 mA (Steel’s test, P < 0.05). There was no statistically significant difference in any particulars other than artifact on images obtained at 180, 150, and 120 mA. By ROC analysis there was no statistical difference in the Az value to identify GGO nodules on images obtained at 180, 150, 120, 90, or 60 mA. However, the Az value at 30 mA was significantly lower than at 180 mA (Dunnett’s test, P < 0.01). Conclusion The minimum current necessary for the characterization of GGO nodules on HRCT was 120 mA, although their identification was possible at currents of >30 mA.     

CT fluoroscopy-guided cutting needle biopsy of focal pure ground-glass opacity lung lesions: diagnostic yield in 83 lesions

Objective

The objective of our study was to retrospectively determine the diagnostic yield of CT fluoroscopy-guided cutting needle biopsy of focal pure ground-glass opacity lung lesions.

Materials and methods

Biopsies were performed using 20-G coaxial cutting needles for 83 focal pure ground-glass opacity lung lesions (mean lesion size, 12.1 mm). After excluding the lesions for which biopsy specimens were unobtainable and final diagnoses were undetermined, the diagnostic yield, including sensitivity and specificity for a diagnosis of malignancy and accuracy, was calculated. The lesions were then divided into 2 groups: the diagnostic failure group, comprising lesions with false-negative results and for which a biopsy specimen was unobtainable; and the diagnostic success group, comprising lesions with true-negative results and true-positive results. Various variables were compared between the 2 groups by univariate analysis.

Results

Biopsy specimens were obtained from 82 lesions, while specimens could not be obtained from 1 lesion. Final diagnosis was undetermined in 16 lesions. The sensitivity and specificity for a diagnosis of malignancy were 95% (58/61) and 100% (5/5), respectively. Diagnostic accuracy was 95% (63/66). The 4 lesions in diagnostic failure group were smaller, deeper, and more likely to be located in the lower lobe and further, for those lesions, number of specimens obtained was smaller, compared with 63 lesions in diagnostic success group. However, none of the differences were statistically significant.

Conclusion

CT fluoroscopy-guided cutting needle biopsy provided high diagnostic yield for focal pure ground-glass opacity lung lesions.     

Focal interstitial fibrosis manifesting as nodular ground-glass opacity: thin-section CT findings

The purpose of this study was to describe the thin-section computed tomographic (CT) features of focal interstitial fibrosis manifesting as nodular ground-glass opacity (GGO) and its changes during follow-up. The thin-section CT findings of pathologically proven focal interstitial fibrosis manifesting as nodular GGO were retrospectively evaluated in nine patients (five women and four men; mean age, 59.3 years; age range, 34–81 years). The thin-section CT findings of each lesion were analyzed for multiplicity, location, shape, margin characteristics, pleural retraction or vascular convergence, size and internal attenuation, lesion internal features and lesion changes on follow-up CT scans (mean 90 days, range 5 to 215 days). All lesions manifested as a solitary nodular GGO (100%), and seven of the nine lesions (77.8%) were located in the upper lobe. Focal interstitial fibrosis was round or oval in shape in five cases (55.6%), complex in shape in three cases (33.3%) and polygonal in one case (11.1%). Lesion margins were smooth in five patients (55.6%), irregular in three (33.3%) and spiculated in one (11.1%). Pleural retraction or vascular convergence was present in two patients (22.2%). Lesions measured 4.8 mm to 25.5 mm (mean, 11.5 mm) and had attenuations ranging from −151 to −699 HU (mean, −514.7 HU). Eight (88.9%) manifested as pure nodular GGOs and one as mixed GGO with a spiculated margin. In all patients, no lesion changes were observed in follow-up CT scans. Focal interstitial fibrosis manifesting as nodular GGO usually presents as a solitary nodule with pure GGO on thin-section CT, which does not change significantly during follow-up.     

Detection of lung cancer on chest radiographs: analysis on the basis of size and extent of ground-glass opacity at thin-section CT

PURPOSE: To evaluate the detection of small peripheral lung tumors on chest radiographs on the basis of the size of the tumor and its extent of ground-glass opacity (GGO) at thin-section computed tomography (CT). MATERIALS AND METHODS: Chest radiographs of 75 patients with peripheral carcinomas 20 mm in diameter or smaller (26 localized bronchioloalveolar carcinomas [BACs], 49 other carcinomas) and 60 normal chest radiographs were retrospectively reviewed individually by 10 radiologists. The extent of GGO within the lesions at thin-section CT was reviewed retrospectively. The detection rates for localized BAC and other carcinomas on chest radiographs were calculated and were correlated with tumor size and extent of GGO. RESULTS: The mean sensitivity for detection of small peripheral carcinomas was 58.5% +/- 8.8 (standard error) for localized BAC and was 78.6% +/- 5.1 for other carcinomas (P =.024). Lesions that were smaller than 15 mm in diameter and had an extent of GGO of 70% or greater at thin-section CT were more difficult to detect than tumors that had larger diameters or less extensive GGO (chi(2) = 8.13, df = 1, P =.004). CONCLUSION: The detection of small peripheral carcinomas on chest radiographs is influenced by tumor size and extent of GGO as seen at thin-section CT.     

肺孤立性磨玻璃密度结节的超高分辨力CT表现及与病理的相关性

目的：探讨肺孤立性磨玻璃密度结节的超高分辨力CT表现及与病理的相关性。方法：搜集经超高分辨力CT（UHRCT）检出并有病理结果的孤立性肺部磨玻璃密度结节（fGGN）72例,72例病灶最大径均≤2cm,回顾性分析其UHRCT表现,并与病理进行对照研究。结果：72例fGGN中纯磨玻璃密度结节（pGGN）20例,混合磨玻璃密度结节（mGGN）52例。20例pGGN中良性病变8例（40％,8／20）,其中炎症3例,局灶纤维化3例,间质或肺泡上皮增生2例;不典型腺瘤样增生（AAH）6例（30％,6／20）,细支气管肺泡癌（BAc）6例（30％,6／20）。52例mGGN中良性病变2例（3．85％,2／52）,其中慢性炎症1例,肺泡内出血1例;恶性病变50例（96．15％,50／52）,其中BACl0例,含BAc的腺癌35例,不舍BAC的腺癌5例。结论：超高分辨力CT影像上,pGGN的病理诊断以良性病变、AAH或BAC为主,而mGGN则大多为BAC及肺小腺癌。     

Meta-analysis of CT-guided transthoracic needle biopsy for the evaluation of the ground-glass opacity pulmonary lesions

Objective:

This meta-analysis is to determine the overall diagnostic yield of CT-guided transthoracic needle biopsy (TNB) of ground-glass opacity (GGO) lesions.

Methods:

A PubMed search was performed using “ground-glass opacity” crossed with “core biopsy” and “needle biopsy”. Test performance characteristics with the use of forest plots, summary receiver operating characteristic curves and bivariate random effects models were summarized. Adverse events, if reported, were recorded.

Results:

Our search identified 52 citations, of which 6 diagnostic studies evaluated 341 patients. Pooled specificity estimates were 0.94 [95% confidence interval (CI), 0.84–0.98] and sensitivity estimates were 0.92 (95% CI, 0.88–0.95), respectively. The positive likelihood ratio was 11.27 (95% CI, 4.2–30.6), the negative likelihood ratio was 0.1 (95% CI, 0.06–0.19), the diagnostic odds ratio was 131.38 (95% CI, 39.6–436.0) and the area under the curve was 0.97.

Conclusion:

Our data suggest that the CT-guided TNB is likely to be a useful tool for tissue diagnosis and may serve as an alternative for further patient management with GGO lesions. However, considering the limited studies and patients included, large scale studies are needed to verify these findings.

Advances in knowledge:

Some studies about CT-guided TNB of GGO lesions have been published, most have been small, single-institution case series. To our knowledge, our study is the first systematic analysis about CT-guided TNB of GGO lesions.Owing to the prevalence of lung cancer screening with low-dose CT, an increase in the detection of ground-glass opacity (GGO) lesions has been noted.^1–3 GGO is a finding on thin-section CT that is defined as “hazy increased attenuation of the lung with preservation of bronchial and vascular margins”.⁴ These characteristics may be caused by partial filling of air spaces, interstitial thickening, partial collapse of alveoli, normal expiration or increased capillary blood volume. It is known that GGO is a non-specific finding that may be caused by various disorders, including inflammatory disease, pulmonary fibrosis, alveolar haemorrhage or neoplasm.^5,6 The clinical significance of localized GGO is its high incidence of malignancy compared with solid nodules.^7,8 Kim et al⁹ reported that approximately 75% of focal pure GGO lesions are adenocarcinoma. Although it has been reported that the morphologic classification is helpful to differentiate malignant GGO lesions from benign conditions,⁸ it is generally considered very difficult based on CT findings alone.⁹ CT-guided biopsy is an established diagnostic technique that has high diagnostic yield and is used mainly for solid lung lesions.^10,11 Although some studies about CT-guided TNB of GGO lesions have been published, most have been small, single-institution case series. Figure 6 shows the procedure of CT-guided TNB for GGO lesions. The aim of this study was to systemically and quantitatively assess the diagnostic performance of CT-guided transthoracic needle biopsy (TNB) of GGO lesions.Open in a separate windowFigure 6.CT-guided core biopsy in 76-year-old male with ground-glass opacity (GGO) lesion in left lower lobe. CT scan obtained during biopsy shows biopsy needle targeting GGO lesion. Histologic diagnosis of core biopsy and surgical resection was adenocarcinoma.     

Multidetector CT features of pulmonary focal ground-glass opacity: differences between benign and malignant

Objective

To evaluate different features between benign and malignant pulmonary focal ground-glass opacity (fGGO) on multidetector CT (MDCT).

Methods

82 pathologically or clinically confirmed fGGOs were retrospectively analysed with regard to demographic data, lesion size and location, attenuation value and MDCT features including shape, margin, interface, internal characteristics and adjacent structure. Differences between benign and malignant fGGOs were analysed using a χ² test, Fisher''s exact test or Mann–Whitney U-test. Morphological characteristics were analysed by binary logistic regression analysis to estimate the likelihood of malignancy.

Results

There were 21 benign and 61 malignant lesions. No statistical differences were found between benign and malignant fGGOs in terms of demographic data, size, location and attenuation value. The frequency of lobulation (p=0.000), spiculation (p=0.008), spine-like process (p=0.004), well-defined but coarse interface (p=0.000), bronchus cut-off (p=0.003), other air-containing space (p=0.000), pleural indentation (p=0.000) and vascular convergence (p=0.006) was significantly higher in malignant fGGOs than that in benign fGGOs. Binary logistic regression analysis showed that lobulation, interface and pleural indentation were important indicators for malignant diagnosis of fGGO, with the corresponding odds ratios of 8.122, 3.139 and 9.076, respectively. In addition, a well-defined but coarse interface was the most important indicator of malignancy among all interface types. With all three important indicators considered, the diagnostic sensitivity, specificity and accuracy were 93.4%, 66.7% and 86.6%, respectively.

Conclusion

An fGGO with lobulation, a well-defined but coarse interface and pleural indentation gives a greater than average likelihood of being malignant.With the availability of low-dose spiral CT scan of the lung, focal ground-glass opacity (fGGO) that was difficult to detect on conventional chest radiographs has increasingly been detected [1-3]. Ground-glass opacity (GGO) is defined as an area of a slight homogeneous increase in density, which does not obscure underlying bronchial structures or vascular margins on high-resolution CT (HRCT) [4]. Pathologically, GGO may be caused by partial airspace filling, interstitial thickening with inflammation, oedema, fibrosis, neoplastic proliferation, the normal respiratory condition or increased pulmonary capillary blood volume [5]. GGO can be classified as pure GGO (pGGO) or mixed GGO (mGGO) based on the presence of solid components. Although GGO is a common and non-specific finding of lung HRCT, and may occur in benign lung conditions such as organising pneumonia, focal fibrosis and haemorrhage [6-8], it has recently received considerable attention because it may indicate an early underlying lung cancer, which in most cases presents as bronchioloalveolar carcinoma (BAC) and adenocarcinoma with a predominant BAC component. It was reported in a study [9] that 17 of 28 pGGOs were BAC, 3 were adenocarcinoma and 8 were atypical adenomatous hyperplasia (AAH). Several other studies [10,11] have also indicated that mGGOs are more likely to be malignant, with the malignant rate of pGGO and mGGO being 18% and 63%, respectively [12]. The aim of the present study was to retrospectively compare the features of benign and malignant fGGOs on thin section multidetector CT (MDCT) images in an attempt to identify characteristics that would help the differential diagnosis of fGGOs.     

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.