폐암의방사선소견 ( 비전형적소견을중심으로 ) 종설 경희대학교의과대학진단방사선과학교실성동욱 Radiological Findings of Lung Cancer: Focus on typical Pattern Dong-Wook Sung, M.D. Diagnostic Radiology Kyung Hee University Hospital, Seoul, Korea The clinical and radiographic findings of lung cancer have been well established many journals. Even if the radiographic findings of lung cancer show a typical pattern, the specific cell type of lung cancer sometimes needs to be determined prior to a pathological diagnosis. For example, the usual finding of a squamous cell carcinoma is similar to other cancer types such as an adenocarcinoma or a small cell carcinoma but with a lower incidence. Therefore, it should not be used to make a diagnosis of the cell type prior to a pathological diagnosis. Many unusual findings of lung cancer, so called atypical pattern have been reported, but atypical findings are widely accepted. The more important thing is not to diagnose a specific cell type of cancer but to differentiate it from other benign conditions such as tuberculosis, fungal infections or organizing pneumonia. This paper presents typical information of the cell type of lung cancer along with the atypical radiographic findings. (Tuberc Respir Dis 2005; 58: 554-561) Key words : Lung neoplasms, Radiography, Diagnosis 서 폐암의임상적및전형적방사선소견에관한설명은잘정리되어여러책이나논문에서소개되고있다 1,2. 전형적소견으로방사선검사에서나타나는경우, 폐암의세포성분까지추측할수있으나, 전형적인소견이어느한가지세포형태의폐암에서만관찰되는경우는없으므로세포성분까지말하려하는오류는범하여서는안된다. 비정형적인소견은그빈도도낮고, 어느경우에는감염성질환의특징적방사선소견으로나타나는경우도있어, 폐암을방사선학적으로진단하려할때는폐암이아니지않을까하는의문과, 역으로감염성질환의특징적방사선소견이더라도혹시폐암이이렇게나타나지않을까하는염두를항상생각하며진단하는습관을가져야한다. 특히조금깊게폐암의각세포별특징을알게되는경우에세포성분까지진단하려고하는과오를범하기쉽다. 폐암의진단에서는세포성분을맞추려는노력보다는다 론 ddress for correspondence : Dong-Wook Sung, M.D. Department of Diagnostic Radiology Kyung Hee University Hospital #1 Hoeki-dong, Dongdaemun-gu, Seoul, 130-702, Korea Phone : 02-958-8616 Fax : 02-968-0787 E-mail : sungdw@khmc.or.kr 른감별진단에더치중하여야한다. 여기서는전형적인소견의기술과더불어, 놓치기쉬운비전형적인소견을중심으로기술한다. 폐암의분류 WHO에의해 1 편평상피세포암 (squamous cell carcinoma) 2 선암 (adenocarcinoma) 3 소세포암 (small cell carcinoma) 4 대세포암 (large cell carcinoma) 의네가지형태의세포형태로구분하고, 이들이전체폐암의 90-95 % 를차지한다 (Table 1) 3. 일반적으로 6:4 의비율로우측폐에많이발생하며, 상엽의전방엽에호발한다. 폐암에서조직학적세포형태를나누는것은그예후에는중요한인자는아니나치료에중요한역할을하기때문이다. 예후는세포형태보다는병기판정에의해결정된다. 편평상피세포암 1. 중심성종괴중심성기관지에서발생하는경우가 65 % 정도이 554
Tuberculosis and Respiratory Diseases Vol. 58. No. 6, Jun. 2005 Table 1. Histologic classification of lung tumors* (1) Squamous carcinoma (epidermoid carcinoma) Variant : Spindle cell (squamous) carcinoma (2) Small cell carcinoma a. Oat cell carcinoma b. Intermediate cell type c. Combined oat cell carcinoma (3) denocarcinoma a. cinar adenocarcinoma b. Papillary adenocarcinoma c. ronchiolo-alveolar carcinoma d. Solid carcionma with mucus formation (4) Large cell carcinoma Variants : a. Giant cell carcinoma b. Clear cell carcinoma (5) denosquamous carcinoma (6) Carcinoid tumor (7) ronchial gland carcinomas a. denoid cystic carcinoma b. Mucoepidermoid carcinoma c. Others (8) Others * WHO classification, 1981 며, 방사선학적으로나임상적으로종괴를발견하지못해도객담검사에서암세포를발견할수있다 (Fig. 1). 기관을막고있는종괴에의해이차적소견이나타나며, 여기에는무기폐, 폐쇄성폐렴이보인다. 대개의경우공기-기관지음영 (air-bronchogram) 이폐쇄성폐렴의내부에보이지않게되며, 이것으로원발종괴를확인하지못하더라도결핵성이나, 감염성폐쇄와감별을할수있다. 재발성폐렴은흉부X선에서종양을발견할수없어도기관지내병변을감별하기위해기관지내시경이필요할수있다 (Fig. 2) 폐쇄성폐렴을치료하지않으면공동이생길수있다. 그외기관지확장증, 점액충전 (mucoid impaction), 체크밸브에의한병변측의공기충만이나타날수있다. 상엽을막는폐암의경우 Golden's S sign을관찰할수있고, 페암에의한골전위로인해골파괴, 종격동구조물의침범, 상대정맥의압박, 폐쇄, 늑간신경의침범으로인한횡격막거상이나타날수있다. 중심상종괴와그이하부위의폐쇄성폐렴을일으키는질환은폐암뿐만아니라, 기질성폐렴 (organizing pneumonia), 폐방선균증 (pulmonary actinomycosis), 결핵때문에나타날수있어, 항상위의질환들을감별해야한다 (Fig. 3). 종괴의변연부는교미침모양 (spiculation) 을할수 Figure 1. Squamous cell carcinoma in a 50-year-old man. CT shows multiple nodular thickening on the posterior wall of the right upper lobe bronchus. Chest P(not shown) was normal, and a malignancy was detected on sputum cytology. 있다. 이는악성, 양성에서모두관찰할수있으나 4, Han 등 5 의보고에의하면폐암에서보이는교미침모양의길이는폐암에서평균 5.7mm, 결핵성육아종에서는 13.8mm로의미있는차이가보이며, 그숫자는차이가없다고하였다. 폐암과결핵성육아종을감별하는한가지방법이될수있겠다. 2. 변연부종괴 편평상피세포암의 30-40 % 에서폐변연부에위치한다. 폐암중에서가장크기가커질수있다. 가끔변연부에서종괴형태를가지지않고결핵성형태, 변연부무기폐모양으로흉막을따라옆으로넓게퍼지는경우가있는데, 이런경우항상폐암의가능성을생각해야한다 (Fig. 4). 주위의골파괴가있으면진단에도움이된다. 다른폐암과는달리공동형성을잘한다. 특히상엽에발생시공동형성을잘한다. Chaudhuri 등 6 의보고에의하면공동을형성한 100예의폐암중 82예가편평상피세포암이었다. 공동의벽은두껍고불규칙한내부벽을가진다. 공동내로돌출하는종양을형성할수있어이를 mural nodule이라한다. 드물 555
DW Sung : Radiographic findings of lung cancer: focus on atypical pattern Figure 2. Squamous cell carcinoma with pneumonia in a 68-year-old man.. Chest P shows an ill-defined opacity on the right lower lung zone, impressed initially pneumonia.. Follow up P after 3 weeks with antibiotic treatment shows consolidation still remaining. C. CT shows an intraluminal mass on the right lower lobe bronchus, and distal postobstructive pneumonia. Figure 3. Variable causes of a similar pattern of a mass like lesion with distal obstructive pneumonitis.,. ctinomycosis in a 45-year-old man. C. Organizing pneumonia in a 62-year-old man. D. ronchial aspergillosis in a 78-year-old man. 556
Tuberculosis and Respiratory Diseases Vol. 58. No. 6, Jun. 2005 C Figure 4. Peripheral type of lung cancer.. CT shows a necrotic mass(squamous cell carcinoma) on the left lower lobe superior segment. The adjacent rib is destroyed. The mass is broad based to the thoracic wall. It has grown mainly lateral rather than into the lung parenchyma., C. CT of a 71-year-old man shows irregular peripheral air-space consolidation on the right lower lobe. ir-bronchograms can be seen within the opacity and it broad based Cto the thoracic wall. It was confirmed as an adenocarcinoma with percutaneous needle aspiration cytology. Figure 5. Cavitary change in a squamous cell carcinoma in a 70-year-old woman.. CT shows a well defined mass with total inner necrosis on the right upper lobe.. CT of the lung setting after 5 days shows a cavitary change in the mass. Its inner wall is smooth, but focal irregular thickening on the medial inferior wall indicates the tumor site. 게공동의벽두께가아주얇아기관지원성낭종 (bro nchogenic cyst) 과감별이필요하다. 이는과다한괴 C 사때문이다 (Fig. 5). CT 로폐암의존재를확인해야한다. 4. 전이 D 3. Pancoast Tumor Pancoast tumor 혹은상구종양 (superior sulcus tumor) 의가장흔한형태이며흉막을가로질러흉벽, 늑골파괴, 후두신경마비, 팔신경얼기 (brachial plexus) 를침범할수있다. 단순흉부X-선촬영에서골파괴를잘인지하지못하는경우가많으므로양쪽폐첨부흉막비후의차이가 5 mm 이상이면주의해야하며반드시 원격전이는잘하지않으나, 부검에서는약 25 % 에서발견된다. 주로간, 부신, 신장, 뼈에전이된다. 선암전체폐암의 25-30 % 를차지하며대개변연부종괴의형태 (60-70%) 로나타난다. 편평상피세포암의감소에비해증가추세에있다. 이는여성에서의선암 557
DW Sung : Radiographic findings of lung cancer: focus on atypical pattern Figure 6. denocarcinoma in a 57-year-old woman. CT(, ) shows enlargement of the mediastinal, hilar and subcarinal lymph nodes, which has a similar pattern to that of a small cell carcinoma. Radiographically, there is an absence of a primary parenchymal mass. 발생이증가하기때문이다. 2. 중심성종괴 1. 변연부종괴선암의 60-70 % 가변연부형태이며, 변연부종괴의 30-40 % 가선암이다. 비호흡기증상으로뼈통증, 허약, 소화불량, 식욕부진이잘나타나며, 종괴의크기가작아도초기에전이를잘한다. 선암은이전에존재한폐의만성질환, 외부의독소, 진폐분진, 화학가스, 석면폐, 마이코박테리아, 진균, 바이러스와도밀접한관계가있다. 방사선소견은둥글거나타원형을이루고대개 4 cm 이내이나, Woodring 등 7 은 4 cm 이상도 50 % 보고하고있다. 종괴의변연부가불규칙하거나, 불분명할수도있다. 방사형햇무리 (corona radiata) 혹은햇살모양 (sunburst appearance) 를취할수있는데이는종괴의침윤혹은결절주변의결합조직반응때문이다. 종괴의내부에공기-기관지음영이보일수있다. 그외소견으로다발성폐종괴를형성할수있으며, 석회화는대부분주변의석회를침식한경우로변연부에치우쳐있다. 수년에걸쳐천천히자랄수있으며혹은몇년간변연부종괴로변화가없는경우도있다. 2-3년간변화가없으면대개의경우, 양성이라판정하는경우가있는데, 아무리양성의소견이보인다하더라도악성의가능성을잊어버려서는안된다 4. 중심성종괴의선암이최근증가하여 30% 에이르고있다. 이는여성에서선암의발생빈도가증가하고, 이세포형태의조직병리학적분류방법이변화한데기인한것이다. 중심성인경우, 편평세포상피암혹은소세포암과같은방사선소견을보일수있다 (Fig. 6). 3. 전이조기에원격전이를잘하고, 흉막침범을잘한다. 흔한전이위치로서종격동, 폐분부, 부신, 간, 뇌신경계, 골수들이다. Sider 등 8 의보고에의하면단일폐결절이있으면서, 종격동에는림프절종대가없고, 오히려흉곽외에전이가있는경우, 선암이가장흔한세포형태 (67%) 라하였다. 한가지알아둘것은흉곽밖에악성종양이있는환자에서단일폐결절이보이면, 원발암이두경부, 방광, 유방, 자궁경부, 식도, 위, 난소이면이단일결절은전이암보다는원발성폐암이따로생긴가능성이높으며, 원발암이 salivary gland, 부신, 대장, 신장, 갑상선, 자궁, 흉선인경우에는단일폐결절이전이암혹은원발성폐암일경우가반반이다. 그러나원발암이 melanoma, 육종, 고환암인경우는폐에생긴단일결절은전이암가능성이높다 9. 558
Tuberculosis and Respiratory Diseases Vol. 58. No. 6, Jun. 2005 Figure 7. Scar cancer in a 71-year-old man.. Chest P shows a diffuse patchy and mottled air-space consolidations on both lungs, which were confirmed to be tuberculosis.. Chest P after 14 years from shows a complete resolution of previous tuberculosis, but an irregular mass on the left mid-lateral lung zone, and mediastinal lymph nodes enlargement. The mass on the left lower lung zone was confirmed to adenocarcinoma. Figure 8. Solid type of a bronchioloalveolar cell carcinoma.. CT shows a mass on the right lower lobe with inner bubbly lucencies.. CT of another patient shows a mass with inner air-bronchograms. 4. 반흔암 (scar carcinoma) 세기관지폐포암 (C) 오래지속되는폐실질섬유화혹은육아종에서발생한종괴를말한다 (Fig. 7). 반흔암이라진단하기위해선조직병리학적으로 hyalined fibrosed tissue 내에고형부위가존재해야하며, 고밀도의 elastic fiber 가관찰되며, antracotic 물질이발견되고, 육안적인반흔의흔적이존재해야반흔암이라진단할수있다. George 등 10 의보고에의하면, 반흔암 19예중선암이 11예 (58%), 편평상피세포암 3 예 (16%), 소세포암 3예 (16%) 이었고, 반흔암이아닌경우는편평상피세포암이 52% 로가장많았다. 선암의한조직학적형태이며, 전체폐암의 1.5-6.5 % 를차지한다. 말초세기관지혹은폐포벽에서기원하여폐조직을간질로해서주변부로퍼져나가는특징이있으며 (lepidic growth), 이때버팀간질반응 (stromal response) 은적어폐포의구조물은정상을유지한다. 젊은이에서잘발생하고비흡연자에서도발생한다. 폐실질의반흔화나미만성간질성염증, 섬유화와도관련이있다. 방사선소견은각기전혀다른종괴의모습을보인다. 단일결절형이가장흔하며 (43 %), 예후 559
DW Sung : Radiographic findings of lung cancer: focus on atypical pattern C D Figure 9. Rapid progression of a bronchioloalveolar cell carcinoma(c).. Initial chest P shows a homogeneous air-space consolidation on the left lower lobe, impressed pneumonia.. Follow up P after 4 days, the consolidation is more aggravated, suggesting an aggravation of the pneumonia with a parapneumonic effusion. Therefore, a chest tube was inserted. C. P after 7 days from shows more aggravation of the consolidation. D. CT shows a low density consolidation on the left lingular and lower lobes. The density is different from that of pneumonia. The CT angiogram sign and focal enhanced parenchymal collapse within the consolidation, which was confirmed to be the pneumonic type of C. 도좋고, 가끔수년동안크기가변화없이아주천천히자란다. 종양으로폐포가채운다하더라도기관지는정상으로통해있어종괴의내부에공기-기관지음영이보인다. 혹은가성공동 (pseudocavity), 공기방울음영 (bubbly lucency) 가나타난다 (Fig. 8). 종격동림프절종대, 전이는거의없다. 대엽성폐렴형태로 30% 에서나타나며, 내부에공기-기관지음영, 공기- 폐포음영, CT 혈관징후 (CT angiogram sign) 들이나타난다. CT에서저음영으로나타나는데, 이는암세포와과다한점액의분비에기인한것이다. 경계가분명하거나불분명한결절 (27 %) 이다발성으로양측폐에나타날수도있다. 작은결절내에공동을형성할수있고결절주위에간유리음영 (ground-glass opacity) 이보일수도있다. 흉막삼출은약 8-10 % 에서발생되며종격동림프절종대는비교적드물며그외무기폐, 기흉, 공동형성, 흉곽외전이를발생할수있다. 흔히종괴내에공기-기관지음영이보이면세기관지폐포암혹은림프종 (lymphoma) 이라진단할수있는데, 결핵성육아종, 기질적폐렴에서도종괴형태를지니며그내부에공기-기관지음영이존재할수있으므로주의해야한다. 다른형태의폐암에서도마찬가지이나, 세기관지폐포암은그진행이마치급성폐렴처럼변화하여나타날수있다. 이때에도 CT를촬영하여폐경화의모양이정상적폐렴과는다른것 Figure 10. Large cell carcinoma in 59-year-old man.. Chest P shows a small nodule on the right upper lobe.. CT shows a lobulated and fine spiculated nodule on the right upper lobe. 으로세기관지폐포암을진단할수있다 (Fig. 9). 대세포암 전체폐암의 15 % 를차지하며빨리자라며 70 % 에서변연부에서발생한다. 선암보다크기가크며종괴의경계가불분명하고소엽성을이룬다. 공동은드물고전이는말기에나타난다. 두가지의아형이있는데심한흡연자에잘나타나고가끔 CE (carcinoembryonic antigen) 가나타나는거대세포암종 (giant cell carcinoma) 과많은양의글리코겐을함유한투명세포암종 (clear 560
Tuberculosis and Respiratory Diseases Vol. 58. No. 6, Jun. 2005 Table 2. Radiographic patterns based on cell type* Radiological symptom Sq. cell Ca.* Small cell Ca. denoca. Large cell Ca. Hilar tumor Peripheral tumor (of these, > 4cm) pical tumor Multiple tumors telectases Pneumonia Liquefaction Mediastinal Lymph nodes 40% 27% (18%) ( 3%) ( 0%) 36% 15% 7% 1% 78% 29% (26%) ( 2%) ( 1%) 17% 22% 0% 13% 18% 71% ( 8%) ( 1%) ( 2.4%) 10% 15% 2% 2% 32% 59% (41%) ( 4%) ( 2%) 13% 23% 4% 10% Note : *Squamous cell carcinoma. Small cell carcinoma. denocarcinoma. ±Large cell carcinoma (from R.G. Fraser, J..P. Pare: Diseases of the Chest, Saunders, Philadelphia 1983) cell carcinoma) 이있다. 이름처럼외형적으로큰폐암을생각하여서는안되며, 크기가작을수도있다는것을염두에두어야한다 (Fig. 10). 다. 폐암의병리조직학적세포형에따른방사선소견을정리하면표 2와같다. 참고문헌 소세포암 ( 귀리세포암종, oat cell carcinoma) 폐암의 20-30 % 를차지하며가장예후가나쁘다. 조기에원격전이를잘해주위림프절, 혈관을빨리침범하여폐증상이나타나기전에전신에퍼진다. 종괴가 Kulchitsky-type 세포에서기원하여내분비성병변을잘동반한다. 특히 inappropriate secretion of adenocorticotropic hormone (CTH) (Cushing syn drome), Eaton-Lambert syndrome ( 근위근육허약, proximal muscle weakness) 이동반한다. 방사선소견으로동측의폐분부나종격동림프절전이로인해중심성종괴로나타나고, 림프절종대는병변의발견시 80% 에서, 부검에서는 100% 에서관찰된다. 실제중심성종괴의 70-80% 가소세포암이다. 원발성폐암이작고, 커진종격동림프절이원발성폐암과융합되어 CT에서도커진종격동림프절만관찰되는경우가많다. 변연부종괴로나타나는경우는 14% 정도이며, 이때는매우악성이높으며미분화된세포로구성되어있다. 약 40% 에서흉막삼출을동반한다. 종괴가단지한쪽흉곽만을침범한경우를제한적형태 (limited type) 라하며수술로치유가가능하다. 뇌전이는진단시 10-15 % 에서보고되고, 골수전이는 50 % 까지이 1. Sider L. Radiographic manifestation of primary bro nchogenic carcinoma. Radiol Clin North m 1990;28: 583-97. 2. Grippi M. Clinical aspects of lung cancer. Semin Roentgenol 1990;25:12-24. 3. Yesner R. Histopathology of lung cancer. Semin ult rasound CT MR 1988;9:4-26. 4. Erasmus JJ, Connolly JE, Mcdams HP, Roggli VL. Solitary pulmonary nodules: part I. morphologic ev aluation for differentiation of benign and malignant lesions. Radiographics 2000;20:43-58. 5. Han TI, Sung DW, Lim SJ, Yoon Y. Spiculation of lung mass on CT: carcinoma vs. tuberculoma. J Ko rean Radiol Soc 1994;31:63-7. 6. Chaudhuri MR. Primary pulmonary cavitating car cinoma. Thorax 1973;28:354-66. 7. Woodring JH, Stelling C. denocarcinoma of the lung: a tumor with a changing pleomorphic character. m J Roentgenol 1983;140:657-64. 8. Sider L, Horejs D. Frequency of extrathoracic metas tasis from bronchogenic carcinoma in patients with normal-sized hilar and mediastinal lymph nodes on CT. m J Roentgenol 1988;151:893-5. 9. Quint LE, Park CH, Iannettoni MD. Solitary pulmo nary nodules in patients with extrapulmonary neo plasms. Radiology 2000;217:257-61. 10. akris GL. Mulopulos GP, Korchik R, Ezdinli EZ, Ro J, Yoon H. Pulmonary scar carcinoma. Cancer 1983;52:493-7. 561