Journal of Mahatma Gandhi Institute of Medical Sciences

REVIEW ARTICLE
Year
: 2014  |  Volume : 19  |  Issue : 2  |  Page : 100--105

What clinician's need to know about imaging features in lung cancer?


Binit Sureka, Mahesh Kumar Mittal, Aliza Mittal, Mukul Sinha, Brij Bhushan Thukral 
 Department of Radiodiagnosis and Imaging, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India

Correspondence Address:
Binit Sureka
Department of Radiodiagnosis and Imaging, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi-110 029
India

Abstract

Bronchogenic carcinoma is one of the most common cancers both in males and females worldwide. Lung malignancies can present with manifestations involving any organ system and also mimic like benign nodules or infective consolidation. Present review highlights spectrum of typical presentations and imaging features of lung malignancies.



How to cite this article:
Sureka B, Mittal MK, Mittal A, Sinha M, Thukral BB. What clinician's need to know about imaging features in lung cancer?.J Mahatma Gandhi Inst Med Sci 2014;19:100-105


How to cite this URL:
Sureka B, Mittal MK, Mittal A, Sinha M, Thukral BB. What clinician's need to know about imaging features in lung cancer?. J Mahatma Gandhi Inst Med Sci [serial online] 2014 [cited 2019 Aug 23 ];19:100-105
Available from: http://www.jmgims.co.in/text.asp?2014/19/2/100/138428


Full Text

 Introduction



Lung cancer is the most common cause of cancer-related death in men and women and is responsible for 1.3 million deaths worldwide annually. In 2013, American Cancer Society's estimates for lung cancer in the United States are about 228,190 new cases of lung cancer (118,080 in men and 110,110 in women) and an estimated 159,480 deaths from lung cancer (87,260 in men and 72,220 among women), accounting for about 27% of all cancer deaths. [1] Overall, the chance that a man will develop lung cancer in his lifetime is about 1 in 13; for a woman, the risk is about 1 in 16. The incidence of developing a lung cancer is much higher for smokers. [1],[2] In India, lung cancer was initially thought to be extremely rare but today, according to Indian Cancer Registry, approximately 63,000 new lung cancer cases are reported each year. The major risk factor for developing lung cancer is tobacco use. However, a significant number of patients with lung cancer have no history of smoking. [3] In India, there were 51,000 deaths due to lung cancer in 2008 (Globocan Report, 2008). Exact estimates of current cancer deaths due to lung cancer are not available yet, despite Indian national cancer registry being started in 1981. Actual figures regarding the magnitude of lung cancer, therefore, may be larger. [4]

 Radiological Features



The role of imaging lies in (i) making the diagnosis, (ii) staging the tumor, and (iii) assessing treatment response. Initial step lies in differentiating pulmonary lesions from pleural lesions. Pulmonary lesions usually have acute angles with the chest wall and engulf the pulmonary vasculature, whereas pleural-based lesions make obtuse angles, displace the pulmonary vasculature, and change its location on respiration. Extrapleural masses displace the extrapleural fat inward and cause rib erosion. Mediastinal masses have their medial margins merging with the mediastinum, may extend into the bilateral hemi thoraces, and lack air bronchogram. Metastasis to the lungs from distant primary can present as multiple nodules of variable sizes. Cavitating metastatic nodules are seen in squamous cell carcinomas and sarcomas. Calcific metastatic nodules are seen from sarcomas and mucinous adenocarcinoma.

Pathologically, there are four types of lung cancer-Squamous cell, adenocarcinoma, large cell, and small (oat) cell carcinoma. During the past 4 decades, there has been a worldwide decrease in squamous cell cancer and a sharp rise in adenocarcinoma. [5] Squamous cell carcinoma is a slow growing, central, and late metastasizing tumor. Adenocarcinoma arises peripherally and is associated with mediastinal lymphadenopathy and distant metastases at presentation. Bronchoalveolar carcinoma (BAC) is a well-differentiated subtype of adenocarcinoma which has a better prognosis. Cavitation is more common in squamous cell carcinoma [Figure 1]. Extensive hilar and mediastinal lymphadenopathy is more common in small cell carcinoma.

Nodules suspicious for malignancy are usually larger than 3 cm, peripheral margins which show irregularity, speculation, lobulation, and notching, presence of pleural tag, amorphous calcification, feeding vessel sign, positive bronchus sign-narrowing of a peripheral bronchus, doubling time of 1-18 months-26% increase in nodule diameter, thick irregular cavity with maximum thickness greater than 16 mm.{Figure 1}

Feature of pneumonia suspicious for lung cancer on imaging are as follows:

Golden S signRound or oval shape of the opacityPneumonia in the common bronchial territoryPneumonia unchanged for more than 2 weeksPneumonia recurring at same siteExpansion of the consolidated lobeDilated fluid-filled bronchiVisible stenosis of the supplying bronchusExpanded lobe with fluid bronchogram sign [Figure 2].

Features of mediastinal invasion are loss of fat planes with the mediastinum, contact of more than 3 cm with the mediastinum, contact of more than 90° with the aorta, and invasion of mediastinal structures [Figure 3] and [Figure 4]. Elevation of hemidiaphragm is an indirect sign of mediastinal invasion on chest X-ray due to involvement of phrenic nerve. [6] Findings of chest wall invasion are obtuse angle of contact with the chest wall and tumor, obliteration of extrapleural fat plane, pleural thickening, presence of extrapleural soft tissue component and rib destruction [Figure 5]. [7] Pleural involvement is suggested by presence of pleural effusion, nodular pleural deposits, and sometimes spontaneous pneumothorax. For lymph node staging, midline nodes such as prevascular and subcarinal nodes are considered ipsilateral lymph nodes. Contralateral (N3) or gross ipsilateral (N2) lymph nodal involvement precludes surgery.{Figure 2}{Figure 3}{Figure 4}{Figure 5}

Pancoast tumors are apical lung cancers with extrathoracic extension also known as superior sulcus tumors. On chest radiographs, superior sulcus tumors appear as an apical lung mass or pleural thickening. Magnetic resonance imaging is useful to diagnose invasion of chest wall, brachial plexus, neural foramina, and subclavian vessels [Figure 6]. [8]{Figure 6}

BAC occurs in two distinct forms solitary pulmonary nodule or in pneumonic form. Nodules may be solid or show ground glass opacity. Bubble like cystic lucencies, stretching with narrowing of bronchi, crazy paving, and computed tomography (CT) angiogram sign are features suggestive of this type of malignancy [Figure 7]. In 2011, new classification system has replaced BAC with four new terms: (a) Adenocarcinoma in situ-which at CT is usually nonsolid; (b) minimally invasive adenocarcinoma-which at CT is mainly nonsolid but may have a central solid component of up to approximately 5 mm; (c) lepidic predominant nonmucinous adenocarcinoma-which at CT is usually part solid, but may be nonsolid or occasionally have cystic components; and (d) invasive mucinous adenocarcinoma-which at CT varies widely from solid to mostly solid to part solid to nonsolid and may be single or multiple. [9]{Figure 7}

Lymphangitis carcinomatosis represents infiltration of pulmonary lymphatics by tumor cells. On X-ray, reticulonodular opacities are seen in lung fields. High-resolution Computed Tomography (HRCT) scan shows nonuniform, nodular thickening of interlobular septa, and bronchovascular bundles [Figure 8].

Liver, bones, brain [Figure 9], and adrenals [Figure 10] are the most common site of metastases in lung cancer. Imaging protocol for evaluation of lung cancer should include scans of upper abdomen for assessment of liver and adrenals. Hematogenous metastases to the bone are usually osteolytic and painful [Figure 11] and [Figure 12]. Atypical sites of metastases include cutaneous, intramuscular, and intraperitoneal region [Figure 13] and [Figure 14]. Cutaneous metastasis is not a common presentation of bronchogenic carcinoma and generally portends a poor prognosis. [10] Rarely, lung cancer can occur in a preexisting interstitial lung disease [Figure 15], pneumoconiosis, connective tissue disorders, and sarcoidosis.{Figure 8}{Figure 9}{Figure 10}{Figure 11}{Figure 12}{Figure 13}{Figure 14}{Figure 15}

Primary treatment of nonsmall cell lung cancer is surgery with adjuvant chemotherapy and/or radiotherapy. Surgery is done for stage 1 and 2 cancers. T3 tumors are also suitable for surgery if there is no lymphadenopathy or metastasis. Small cell lung carcinomas are treated with radiotherapy or radiofrequency ablation if the patient is unfit for surgery. [11] With the advent of targeted therapies, the latest classification recommends that pathologists minimize the use of the term nonsmall cell lung cancer to better inform the treatment decision of medical oncologists. Pemetrexed in combination with cisplatin is indicated for advanced stage nonsquamous nonsmall cell carcinoma, while bevacizumab is contraindicated in squamous cell carcinoma because of its association with fatal hemorrhage in patients with squamous cell histology. [12]

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