Which finding on CT scans are characteristic of small cell lung cancer (SCLC)?

Updated: Sep 12, 2019
  • Author: Abid Irshad, MD; Chief Editor: Eugene C Lin, MD  more...
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CT scanning is the modality most commonly used for the evaluation and characterization of an abnormality depicted on a chest radiograph. CT is used to assess the size or volume of the tumor, mediastinal involvement, pathologically enlarged lymph nodes, and vascular invasion. It is also sensitive in detecting pleural and pericardial effusion or thickening. Nodularity of pleura or pericardium is the hallmark of metastatic involvement. (See the images below.)

Lung cancer, small cell. Contrast-enhanced CT scan Lung cancer, small cell. Contrast-enhanced CT scan of the chest shows a large left lung and a hilar mass, with invasion of the left pulmonary artery.
Lung cancer, small cell. Contrast-enhanced CT scan Lung cancer, small cell. Contrast-enhanced CT scan of the abdomen. Axial section through the liver shows multiple hypoattenuating areas in the liver. Poorly defined margins, attenuation greater than that of water, and scattered distribution in a patient with known lung cancer is most consistent with metastatic disease.
Lung cancer, small cell. Nonenhanced CT scan of th Lung cancer, small cell. Nonenhanced CT scan of the abdomen at the level of adrenal gland shows a large adrenal mass on the left side. The high attenuation values on this image and the large size of the adrenal mass suggest a malignant lesion. The adrenal glands are a common site for metastatic small-cell lung cancer.
Lung cancer, small cell. CT scan of the chest at t Lung cancer, small cell. CT scan of the chest at the level of hila shows a large hilar tumor on the right side, with loculated pleural effusion. Nodular thickening of the pleura suggests pleural metastasis. The tumor mass is difficult to differentiate from the adjacent atelectatic lung.
Lung cancer, small cell. Axial CT scan though the Lung cancer, small cell. Axial CT scan though the lungs show a solitary pulmonary nodule in the peripheral part of the right lung. Small-cell lung cancer occasionally appears as a peripheral lung nodule.

Contrast-enhanced CT can sometimes be used to differentiate a tumor mass from the adjacent collapsed lung or pneumonitis, which usually enhances more than the tumor. Sometimes, air bronchograms are observed. Three-dimensional (3D) images reconstructed from thin sections through the mass improve the sensitivity in detecting invasion of adjacent organs. Chest wall invasion can be demonstrated with evidence of rib destruction (the most specific finding), pleural thickening, and obliteration of the extrapleural fat line. An obtuse angle of the mass with the chest wall may also suggest invasion. Pain in the chest wall is a more specific sign of involvement.

Similarly, contact with the mediastinum of more than 3 cm, contact with aorta of more than 90°, invasion of the mediastinal fat, and pleural or pericardial thickening are considered signs of mediastinal invasion. CT scans can also show endobronchial growth and the degree of compression of the bronchi or vessels.

The CT scans of patients with SCLC of less than 3.0 cm in size may show notching more frequently than those of patients with adenocarcinoma, whereas surrounding ground-glass opacity, air bronchogram, pleural indentation, and spiculation are observed less frequently in SCLC than in adenocarcinoma. [34]

The size of lymph nodes is generally estimated for staging purposes by measuring the short axis of the lymph nodes. Compared with the long axis, the short axis is a more accurate predictor of the volume. For practical purposes, a short-axis measurement greater than 1 cm is generally considered abnormal in the chest. However, some have observed different measurements in different groups of patients.

CT of the chest routinely includes imaging of the adrenal glands, which are common sites for small cell lung cancer metastases. A lesion with an attenuation value less than 10 HU (Hounsfield units) on a nonenhanced CT scan most likely represents an adenoma (90% accuracy). CT of the abdomen and pelvis is also generally indicated in staging of small cell lung cancer to rule out metastases to the liver, nodes, or other organs. CT of the head helps rule out brain metastasis, which is also common in SCLC. [20] CT is also routinely used to follow up patients with SCLC after irradiation and chemotherapy.

In one study by Kobayashi et al, high-resolution CT (HRCT) features of peripherally located SCLC were retrospectively reviewed in 33 patients with peripherally located SCLC measuring 30 mm or less, and it was determined that a non-round shape and thickening of the bronchovascular bundle (BVB) were common, while marginal ground-glass opacity (GGO) and air bronchogram were less common in small-sized, peripherally located SCLC. In addition, the vermiform/branching shape and thickening of the BVB suggested relatively advanced disease. [35]


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