Neoplasms, metastases and lymphangitic carcinoma

Neoplasms

Lung cancer is one of the commonest types of cancer in men. Smoking and air pollution are important causes. The most common histological types are:
- squamous cell carcinoma
- adenocarcinoma (including alveolar cell tumors)
- small cell carcinoma
- large cell carcinoma

The histological classification is of significance because small cell carcinoma is treated differently from the other types; therefore, lung carcinoma is classified as small cell or non-small cell. The histology cannot be deducted with certainty from chest films, although the different types of tumor may have certain characteristics.

Squamous cell carcinoma often starts centrally, while adenocarcinoma starts as a peripheral tumor. The border of peripheral tumors is often irregular, with lobulation and outgrowing strands. Cavities are common, while calcification is unusual. Alveolar cell tumors may start as solitary round shadows. The cells tend to line the alveolar walls and fill the alveoli instead of destroying them. They may therefore look like multiple opacities with indistinct borders, sometimes confluent, and may be confused with bronchopneumonia.

In small cell carcinoma, there is often visible mediastinal widening when the diagnosis is first made (Fig. 51). Unlike squamous cell carcinoma, there is no necrosis in small cell tumors.

The first finding in a central tumor is often a pneumonic opacity, as stagnation of secretion peripheral to an endobronchial tumor disposes to infection. The picture may become normal again with adequate treatment of the pneumonia, since the tumor itself is not large enough to be visible, or is hidden by the mediastinal shadow. Recurrent pneumonia or atelectasis of the same lobe must result in cancer being suspected and

Figure 51. CT section of the thorax in a patient with small cell pulmonary carcinoma. Spreading to the mediastinum at the time of diagnosis. Descending aorta (A), pulmonary artery (P), tumor (T). Small right- sided pleural effusion.

lead to bronchoscopy.

It is important to obtain tissue for biopsy, and this is done either using bronchoscopy or by needle puncture through the chest wall under the guidance of fluoroscopy. When the diagnosis of cancer is established, an attempt is made to classify the tumor by assessing the size and possible growth into the adjacent organs. A search for lymph node metastases, and distant metastases is also performed.

On the chest radiograph, the presence of the following should be assessed systematically:
- Central or peripheral tumor
- Invasion of the hilum or mediastinum

CT scan has become a routine method of assessing invasion of the medastinum. The layers of fat in front of the trachea and carina, the subcarinal area, and the aortopulmonary "window" (between the aortic arch above and the pulmonary artery below) are all inspected. MR! has been found to be particularly effective for demonstrating invasion of central cardiovascular structures (Fig. 10).
- Pleural fluid

Malignant cells in pleural fluid are a poor prognostic sign.
- Invasion of the chest wall (Fig. 5) with destruction of ribs.
- A special type of carcinoma (Pancoast or superior sulcus tumor) is squamous cell carcinoma in the apex of the lung, destruction of the upper ribs and involvement of the brachial plexus. These patients may have shoulder pain as the first symptom and be referred for radiotherapy of the shoulder. The extent of these tumors is now optimally evaluated by MRI using sagittal and/or coronal planes to determine penetration of tumor through the apical fat pad with possible involvement of the brachial plexus, chest wall, or neck (Figs. 8, 9).
- Elevated diaphragm

If fluoroscopy shows paradoxical motion, this indicates invasion of the mediastinum with involvement of the phrenic nerve and paralysis of the ipsilateral dome of the diaphragm.
- Metastases to the contralateral lung or ribs
Such findings in the chest film may save the patient from further diagnostic examinations and thoracotomy.

Metastases

Pulmonary metastases may be solitary or multiple (Figs. 37,49). They are often globular with a smooth surface. When multiple, the sizes differ from one les ion to another. Most metastases are near the surface of the individual lobe of the lung (including those that lie close to the interlobar fissure ). Preoperative CT scan is necessary in patients with presumably solitary metastases. It will then be possible to detect additional metastases located near the mediastinum or in the sinus posteriorly.

Lymphangitic carcinoma

When cancer cells spread to the mediastinal lymph nodes, obstruction to the flow of lymph from the lung towards the hilum may occur, and cancer cells may grow along the lymph vessels peripherally. On thoracic radiographs, this phenomenon will appear as radiating strands from the hilar region, and the strands will be accompanied by thickening of the peripheral interstitial septa. This condition often develops gradually, unlike interstitial edema caused by heart failure where the symptoms often develop more rapidly.

Alf Kolbenstvedt, Arnulf Skjennald and Charles B. Higgins