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Chapter Ten -- Tumor and Tumor-Like Processes of the Lung, Pleura and Mediastinum


Introduction and Interesting Links
Chapter One - Methods of Examination

Chapter Two - Normal Radiographic Anatomy
Chapter Three - Normal Variants and Congenital Anomalies
Chapter Four - Signs of Disease
Chapter Five - Acute Pulmonary Infections
Chapter Six - Pulmonary Tuberculosis
Chapter Seven - Pulmonary Sarcoidosis
Chapter Eight - Metastatic Disease and Related Conditions
Chapter Nine - The Solitary Pulmonary Nodule
Chapter Ten - Lung Carcinoma and Related Conditions

Chapter Eleven - Pneumothorax
Chapter Twelve - COPD
Chapter Thirteen - Heart and Great Vessels

Chapter Ten: Tumor and Tumor-Like Processes
of the Lung, Pleura and Mediastinum

In this chapter we will cover:

  • Lung Carcinoma and Related Conditions
  • Pleural-Based Tumors
  • Mediastinal Masses

Lung Carcinoma and Related Conditions

The four main cell types of bronchial carcinoma are:

    • squamous cell (also known as epidermoid)
    • adenocarcinoma
    • large cell anaplastic
    • small cell (also called oat cell)

All but adenocarcinoma have a strong association with smoking.

Since small cell carcinoma is so very nasty (median survival after diagnosis is only two to four months), the most practical classification system of lung carcinoma is: small cell lung carcinoma and non-small cell lung carcinoma -- SCLC and NSCLC. Squamous cell, adenocarcinoma and large cell carcinoma are NSCLC.

The TNM system is used for staging for NSCLC -- which helps determine viable treatment options.

    • Tumor--size and involvement of adjacent structures
    • Nodes--whether or not local or distant lymph nodes are affected
    • Metastasis--local or distant spread of the cancer

Radiographic manifestations of lung carcinoma.

  • A mass or nodule
  • Recurrent pneumonia
  • Volume loss, Goldens "S" sign
  • Cavitation
  • Pancoast's syndrome
  • Paraneoplastic syndrome

A mass or nodule.
Nodules are smaller than 4 cm in diameter. A mass exceeds 4 cm. About 60% of all lung nodules or masses are located centrally, that is, close to the lung hilus. The lung hilus is notoriously difficult to read. It's easy to miss small nodules here. For better or worse, however, the closer a nodule is to the root of the lung, the earlier it may manifest clinically and potentially lead to earlier diagnosis. Unfortunately the survival rate for most lung cancer is still fairly dismal.

Conversely about 40% of lung cancers are located peripherally. In theory these should be more easily identified without overlying hilar or mediastinal components. When a nodule or mass is peripheral, though, it is less likely to cause symptoms, so the individual may not show a need for radiographs.

(See Chapter Nine for more information on the Solitary Pulmonary Nodule.)

Recurrent pneumonia.
This is an ominous clinical sign, particularly in smokers. The airway becomes partially or completely obstructed by tumor, secretions are unable to clear leading to infection. A radiograph at the time of the pneumonia usually will not reveal the actual tumor because it will be obscured by consolidation. After the pneumonia clears, a follow-up radiograph should be taken to help disclose the presence of an underlying nodule or mass.

Volume loss (atelectasis).
Obstruction atelectasis occurs when the lumen of a bronchus is occluded. Signs of atelectasis include:

    • Direct Signs
      • Increased density
      • Bronchovascular crowding
      • Deviation of a fissure
    • Indirect Signs
      • Hilar displacement
      • Tracheal deviation
      • Shift of the mediastinum
      • Elevation of a hemidiaphragm
      • Rib approximation
      • Compensatory hyperaeration

(See Chapter Four for more information on atelectasis.)

Golden's "S" sign is a specific form of volume loss in which the right upper lobe bronchus is affected. The horizontal fissure is elevated peripherally, but the mass growing within or near the right upper lobe bronchus is responsible for keeping the medial portion of the fissure down.

Cavitation.
When a mass enlarges to the point that it outgrows its blood supply, part of the tumor may undergo necrosis. This results in cavitation which is usually a late finding in lung carcinoma, particularly common in squamous cell. A cavity within the mass is distinctive radiographically because of an air-fluid level which can be seen on upright views or cross-table views, i.e. lateral decubitus. Other conditions which may cause cavitation are tuberculosis, some fungal infections, hydatid cysts and staphylococcal pneumonia.


Cavitation of large mass in left lung.

 

Pancoast Syndrome.
A superior sulcus tumor, as it is also known, can manifest clinically with musculoskeletal symptoms and signs. This is why chiropractors must know to look for Pancoast syndrome. Shoulder pain, neck pain and muscle wasting in the distribution of C8, T1 or T2 nerve roots can be the presenting complaints. These manifestations may be present for years before the true diagnosis is revealed. Also, since the sympathetic chain may become involved, Horner's syndrome can occur: ptosis, miosis and hemianhydrosis.


Ptosis of eyelid, miosis (constriction of pupil), and inability to sweat (anhydrosis) on shaded side of face


Radiographically an apical soft tissue mass may be visible, though the earliest manifestation of the soft tissue component is simply apical pleural thickening.

Remember that reactivation TB occurs in the lung apex, too. Both can manifest as pleural thickening or increased density. TB will usually show signs of atelectasis, while a Pancoast tumor will have a mass effect on the adjacent soft tissues. The tracheal air column, for instance, might displace toward TB and away from Pancoast tumor.

The bones at the cervicothoracic junction should be carefully evaluated for subtle evidence of destruction. This destruction is due to local metastatic spread from the primary tumor. Moth-eaten to permeative destruction with loss of cortical outline are the main findings. This can occur in the vertebrae and the ribs.


Pancoast tumor left apex.

Same patient. Low kVp film shows bone destruction.

 

Pleural-Based Tumors

Mesothelioma is the most common pleural tumor. There are two forms of mesothelioma: localized and diffuse. Localized mesothelioma is not related to prior asbestos exposure and is very rare. Diffuse mesothelioma has a strong association with asbestos exposure which might have occurred several decades before mesothelioma arises.

The types of individuals who routinely were exposed to asbestos are:

  1. Shipyard workers. These people worked deep within the bowels of ships where the very close quarters and poor ventilation permitted them to come into close contact with the asbestos insulation pipes.
  2. Automobile mechanics. Some brake linings are still made with asbestos.
  3. Pipefitters.
  4. Maintenance workers.
  5. Family members of the above can be exposed through the contaminated clothing or hair of the worker.

Asbestos is a mineral with a very high melting point from which fibers can be extracted and woven into fabric and other textiles. It has been used for over 100 years in applications where heat buildup can be detrimental to most other substances. Its use peaked in the 1970's. The fibers are very light and tiny. Because of their size and shape (like tiny needles), they can be drawn in all the way to the alveolar wall. The cilia in the air passages are not able to prevent this migration. At the alveolus, macrophages attempt to engulf the fiber for clearing, but don't succeed. They die, spilling their lysosomal enzymes and cause fibrosis. This continues to build until the pleura are thickened. Most exposed individuals do not develop diffuse mesothelioma. It is thought that a DNA-tumor virus is responsible along with the exposure.
Click here for a picture of an individual asbestos fiber.

Radiographic features of diffuse mesothelioma.
The plain chest x-ray may reveal multiple, well-defined masses which, when oriented tangential to the x-ray beam, will demonstrate an extrapleural sign. CT scans are most effective at delineating the tumors and can help determine whether there is involvement of the chest wall and/or ribs.


Mediastinal Masses

The anatomic boundaries of the mediastinum are defined in a variety of ways.

The most practical division is this:

The anterior mediastinum extends from the posterior sternum to the pericardium of the anterior heart; the middle mediastinum extends from this boundary to the posterior margin of the same structures (it IS the heart, the ascending aorta, brachiocephalic vessels, left common carotid and left subclavian artery); and the posterior mediastinum lies posterior to the heart. The superior mediastinum is included with the anterior mediastinum for practical purposes, though an anatomist would define the superior mediastinum as that region above the level of a line drawn between the manubriosternal junction and the bottom of the fourth thoracic vertebra.


Most practical division combines the anterior with the superior portions of the mediastinum.

The superior mediastinum as defined by anatomists.

THE ANTERIOR MEDIASTINUM.
Approximately 60% of mediastinal masses occur. The space is very small and normally contains only fat, lymphoid tissue, residual thymic tissue and connective tissue. The common anterior mediastinal masses are:

  1. Thymoma
  2. Substernal thyroid (goiter)
  3. Teratoma
  4. Lymphoma

Radiographic features of anterior mediastinal masses.


Filling in of the retrosternal clear space.

Widened appearance of the upper mediastinum.
  • Filling in of the anterior (retrosternal) clear space. This is demonstrated on the
    lateral projection.
  • Widening of the upper mediastinum. This is demonstrated on the PA projection.


Normally the plain radiographic features do not permit differentiating one type of mediastinal mass from another. Occasionally a tooth may be visible in a teratoma to help form a diagnosis of a germ-cell tumor.

 

THE MIDDLE MEDIASTINUM.
Only 15% of all mediastinal masses arise in the middle mediastinum. Anterior mediastinal masses often displace normal middle mediastinal components, such as the trachea. The middle mediastinum also consists of the heart, pericardium and lymph nodes. Heart tumors are very rare.


THE POSTERIOR MEDIASTINUM.

The remainder of mediastinal masses, about 25%, occur in this compartment. The components are: descending thoracic aorta, esophagus, lymph nodes and the paraspinal region. Most posterior mediastinal masses are of neurogenic origin such as Schwannoma, neurofibroma and the like. Aneurysms of the descending thoracic aorta can simulate a mass, particularly saccular types.


    Posterior mediastinal mass. Dx: Neurofibroma.

    Same patient.
    Note the posterior location.


    Note close
    relationship to spine.



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