J Korean Radiol Soc 1998; 39: 693-698 Solitary Nodular Bronchioloalveolar Carcinoma ofthe Lung: 1 Prediction ofHistology at High-Resolution CT Hyun-JungJang, M.D., Kyung Soo Lee, M.D., Yookyung Kirn, M.D. 2 Myung-HeeShin, M.D.3, In Wook Choo, M.D., SeungHoonKirn, M.D. WonJae Lee, M.D., Hong SikByun, M.D., SangJinKirn, M.D.4 Purpose : The purpose of this study is to describe the characteristic high-resol­ ution (HR) CT findings of solitary nodular bronchioloalveolar carcinoma (BAC) of the lung which are valuable for specific diagnosis ofthe disease. Materials and Methods : HRCT scans of 46 patients (31 with malignant and 15 with benign lesion) with a solitary pulmonary nodule seen on chest radiograph were distributed in random order and analyzed retrospectively. Two blinded observers jointly analyzed the marginal and internal characteristics of nodules as seen on HRCT, and decisions on the findings were reached by consensus. Stepwise discriminant analysis for characteristic findings ofBAC was performed. Results : The most frequent CT findings ofBAC (n= 15) were internal bubble lu­ cency (1 4/15, 93 %)(p=O .-OOl), area of ground-glass opacity (12/1 5, 80 % ; average 58 % of tumor volume)(p=O.OOOl), pleural tag(12/15, 80 % ; p=0.097), and lobulated and spiculated margin(8/1 5, 53 % ; p=0.459). Findings of ground-glass opacity (p=O.OOOl) and bubble lucency (p=0.0187) appeared to be discriminant in the diagnosis of BAC. Conclusion : Peripheral pulmonary nodules containing an area of ground-glass opacity associated with internal bubble-lucency are characteristic ofBAC. Specific histologic diagnosis of solitary nodular BAC can be suggested by careful analysis ofHRCT findings. Index words : Lung, CT Lung, nodule Lung neoplasms, diagnosis Lung neoplasms, CT Bronchioloalveolar carcinoma (BAC) of the lung is a type(7, 8). With its favorable prognosis and distinctive subtype of adenocarcinoma(1 - 4). Its unique features radiologic features, solitary nodular BAC, the most are its histologic lepidic growth pattern using the al­ commonly presenting form, is generally considered a veolar septa as a stroma and its mode of aerogenous separate clinical entity(5, 7, 9). Reported CT findings of spread(5 -7). BAC displays a broad spectrum ofradi이­ solitary nodular BAC include a peripheral subpleural ogic features that can be categorized as solitary nodu­ location, internal bubble lucency or pseudocavitation, lar, segmental or lobar, or the diffuse multinodular heterogeneous attenuation, irregular margins and pleural tag. These findings are not specific, however, 'Department of Radiology, Samsung Medical Center, College of Medicine, Sung they are frequently observed in adenocarcinoma and Ky un Kwan University 'Department of Diagnostic Radiology, College of Medicine, Ewha W omans Uni. large cell carcinoma ofthe lung(lO). versity In over 70 % of patients, nod ular BAC less than 3 cm JDepartment of Center for Health Promotion, Samsung Medical Center 'Department of Diagnostic Radiology, Yongdong Severance Hospital in diameter responds to surgery (ll) and when less Received November 3, 1997; Accepted July 24, 1998 than 2cm, the reported five-year survival rate is 98. 2 Address reprint requests to : Kyung Soo Lee, M.D. , Department of Radiology %(3). Early recognition is therefore important. In a re­ Samsung Medical Center, # 50 Irwon.Dong, Ka ngnam-Ku Seoul 135.230, South Korea. Tel. 82. 2.3410.2511 Fax.82. 2.341O. 2559 cent study involving a small number of patients, we - 693 Hy un-Jung Jang. et al : S이 itary Nodular 8ronchioloalveolar Carcinöma of the Lung reported that a localized area of ground-glass opacity, Image interpretation with internal bubble lucency on high-resolution CT The HRCT scans of all patients were randomly dis­ (HRCT), is an early finding of BAC(12). The result of 2- tributed and assessed by two experienced chest radiol­ [fluorine-181-fluoro-2-deoxy-D-glucose (FDG) positron ogists, whose decisions were consensual. Observers emission tomography(PET), however, may be nega­ had no knowledge of clinical or pathologic data other tive(12 - 14). In addition, presumably because of spar­ than the age and sex of the patients; they were not se cellularity, we have experienced false negative aware of which diseases were included in the study results of percutaneous needle aspiration biopsy of nor, the frequency ofindividual diseases. these lesions. So as not to overlook this surgically The evaluated HRCT findings included the follow­ curable disease, solitary nodular BAC needs to be ings : (a) size (b) edge, classified as smooth, lobulated, recognized, if possible, on the basis of specific imaging spiculated, or lobulated and spiculated; the presence features. of (c) open bronchus sign, (d) positive bronchus sign, The aim of this stud y is to determine the findings (e) bubble lucency, (f) pleural tag, (g) satellite lesion, (h) which most effectively discriminate between solitary air-crescent sign, (i) ground-glass opacity and the per­ nodular BAC and other pulmonary nodules. Our ap­ centage of the nodule it accounted foι estimated visu­ proach involves the use of HRCT followed by stepwise ally; and (j) calcification and its characteristics, classi­ discriminant analysis. fied as central, laminated, popcorn-like, nodular, or stippled. Open bronchus sign (previous CT air bron­ chogram) was considered to be present if there was Materials and Methods patent branching airway structure(s) within a nodule Selection of patients and image acquisition (15, 16). Positive bronchus sign was regarded as pres­ This study involved 46 patients in whom solitary ent if a bronchus extended up to, and entered the nod­ pulmonary nodules were seen on chest radiographs, ule(17). Bubble lucency was considered to be present if and who underwent HRCT between November 1994 there were small scattered areas of air attenuation (oval and May 1997. Nodules were consecutively proved by or round) within a nodule(15). 'Pleural tag' was de­ surgery and satisfied the following inclusion criteria fined as linear structure(s) originating from the margin on chest radiographs: less than 3 cm in maximal dimen­ of a nodule and extending peripherally to contact the sion, a location peripheral to that of segmental bronchi, pleural surface. ‘Satellite nodule' was defined as one or and with no enlarged hilar or mediastinal lymph more micronodule(s) surrounding the dominant nod­ nodes. The patients were 20 men and 26 women, and ule. 'Air-crescent sign' was defined as curvilinear air were aged between 16 and 78 (mean, 58.8) years. All density around a nodule. underwent surgery and definite diagnoses were made on the basis of histopathologic examination of spec­ Statistical analysis imens. Pathologic entities included lung cancer(n=30) Using the chi square test, the frequency of each CT ; BAC(n = 15), adenocarcinoma(n = 11), squamous cell finding of BAC was compared with that of other carcinoma(n=2), large cell carcinoma(n=l), and muc­ nodules. A p-value less than 0.05 was considered sig­ oepidermoid carcinoma(n=1), and benign nodules(n= nificant. 16); aspergilloma(n=7), hamartoma(n=5), and tub­ Age, sex, and CT features were evaluated using step­ erculoma(n =4) wise discriminant analysis; this identifies the discrim­ For CT examinations, a GE HiSpeed Advantage scan­ inant CT findings that most accurately measure the ner (General Electrical Medical Systems, Milwaukee, characteristics of solitary nodular BAC 뻐 d permit dif­ WI, U.S.A) was used. Before obtaining conventional ferentiation between various cell types of lung cancer CT images using the helical technique (lO-mm and benign nodules. The objective is to maximize sep­ collimation, pitch of one) with administration of con­ aration of groups by weighting and combining the trast(lOOmL of Iopamiro 300: IopamidoL Bracco, Mil­ discriminant variables in some linear form. A user-sel­ an, Italy), thin-section (1-mm collimation) CT scans of ected criterion is applied, and the single best discrimi­ all patients were obtained at 3-mm (n=19) or 5-mm nating variable is selected. All remaining potential var­ (n=27) intervals throughout the nodule. Scan data iables are then tested(18, 19). In this study, the ability were reconstructed using a bone algorithm(HRCT). to classify cases correctly using the discriminant func­ Images were obtained both at mediastinal (WW: 400, tion was measured using Fischer’s exact test. The mag WL: 30) and lung window (WW: 1500H, WL: -700) nitude of the coefficient in the resulting discriminant settings. function reflects the unit of measurement as well as its - 694 J Korean Radiol Soc 1998; 39 : 693-698 relative contribution. SAS software (system for Win­ 05. Calcification was stippled. dows version 6.11) was used Stepwise discriminant analysis showed that areas of ground-glass opacity (p=O.OOOl) and bubble lucency (p=0.0058) individually were useful for distinguishing Results BAC from other cell types of lung cancer and benign Solitary nodular BAC was found in seven men and lesions(Table 2). eight women, aged between 39 and 72 (mean, 59) years The BAC ranged in size from 1. 5 to 3.0 (mean, 2.4)cm. Discussion The most frequent CT findings of BAC were internal bubble lucency (14/1 5, 93 %) (p=O.OOI) (Figs. 1 and 2), Kuhlman et al (10) reviewed the thin-section CT area of ground-glass opacity (1 2/15, 80 %, [average 58 (2 - 5 mm collimation) findings of solitary nod ular BAC % of tumor volume]) (p=O.OOOI) (Figs. 1-3), pleur­ in 30 patients. In their series, peripheral or subpleural altag (12/15, 80 %) (p=0.097) (Figs. 1 and 3), and lob­ location(25/30, 83 %), irregular margins forming a star ulated and spiculated margin (8 /1 5, 53 %) (p=0.459) pattern(22/30, 73 %), pleural tag(70 %), pseudocavita­ (Figs. 1 and 3) (Table 1). Open bronchus sign, positive tion(18/30, 60 %), and heterogeneous attenuation (17 / bronchus sign, calcification, and satellite nodule were 30, 57 %) were suggested CT criteria for solitary nodu­ seen in four(27 %), three(20 %), one(7 %), and one (7 %) lar BAC.