Tumors of the lung
* About 90% of lung tumors are bronchogeic carcinomas.
* About 5% are bronchial carcinoids.
* 2 to 5% are mesenchymal and other neoplasms.
I: Bronchogenic Carcinoma
* It is the most common visceral malignancy in males.
* In females, the incidence is increasing, and the lung cancer has passed breast carcinoma
as a cause of death in women.
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* Etiology and pathogenesis:
1. Tobacco Smoking
- Statistical evidence:
* Average smokers of cigarettes have tenfold greather risk of developing
lung cancer, compared with non-smokers.
* There is tatistical association between the frequency of lung cancer,
and the amount of daily smoking, and the duration of the smoking
habit.
* 80% of lung cancers occur in smokers.
* Cessation of smoking for 10 years reduce risk to control level.
- Clinical evidence:
* Hyperplastic and atypical changes in the lining epithelium of the
respiratory tract, occur in about 10% of smokers.
- Experimental evidence.
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2. Industrial hazards:
- There is increased risk of respiratory cancer among persons who
work with Uranium and all types of radiation, Asbestos, Nickel,
Chromates, Coal, Arsenic…..
3. Air pollution:
- Atmospheric pollutants may play some role in the increased incidene
of bronchogenic carcinoma.
4. Genetic factors: Not proved.
5. Scarring:
- Some lung cancers (usually adenocarcinoma) arise in the vicinity of
pulmonary scars.
* Morphology:
- Bronchogenic carcinomas arise most often in and about the hilus of the lung
(Large bronchi).
- It usually starts as an in situ cytologic atypia, then it yields a small area of
thickening of bronchial mucosa.
- Then it enlarges to produce an itraluminal mass, into the bronchial lumen,
infiltrates along the peribronchial tissue, or extends to the pleura and then to
pericardium.
- Spread to the tracheal, bronchial, and mediastinal lymph nodes, can be found in
most cases.
- Spreading widely throughout the body, and at an early stage is very common.
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* Histologic classification:
1. Sqamous cell carcinoma: 35 – 50 %.
2. Adenocarcinoma: 15 – 35 %
3. Small cell Carcinoma: 20 – 25 %
4. Large cell carcinoma: 10 – 15 %
* Histopathology:
1. Squamous cell carcinoma:
- Most common in men, and most closely correlated with a smoking history.
- It has a high rate of growth, tends to spread locally, and metastasize somewhat
later.
2. Adenocarcinoma:
- Two forms:
* The usual bronchial-derived adenocarcinoma.
* The bronchioloalveolar carcinoma, which arises from the terminal
bronchioles or alverolar walls.
- Equal frequency in males and females.
- Grow more slowly than squamous cell type.
- Less frequently associated with a history of smoking.
3. Small ell carcinoma:
- Highly malignant variant which metastasizes widely.
- Has a strong relationship to smoking.
- Commonly associated with ectopic hormone production.
4. Large cell carcinoma.
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* Secondary pathology and complication:
- Partial obstruction of the airways may cause emphysema, total obstruction may lead to
atelectasis.
- The impaired drainage of the airways is a common cause for severe suppurative
bronchitis, bronchiectasis, or pulmonary abscesses.
- Compression or invasion of the superior vena cava may lead to marked venous
congestion.
- Extension to the pericardial or pleural sac may cause pericarditis or pleuritis with
significant effusion.
* Staging:
- The TNM system for staging cancer according to its anatomic extent at the time of
diagnosis is extremely useful.
Occlut:
Bronchopulmonary secretions contain maligant cells, but there is no other evidence of
lung cancer (TX NO MO).
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Stage I:
Tumor 3 cm. or less (T1), with or without involvement of the ipsilateral hilar lymph
nodes, or a tumor over 3 cm., without any nodal involvement (T1 NO MO, T1 N1 MO,
or T2 NO MO).
Stage II:
A tumor over 3 cm., with involvement of the ipsilateral hilar nodes (T2 N1 MO).
Stage III:
Any tumor invading the pleura and adjacent structures, or involving the contralateral
mediastinal nodes, or exhibiting distant metastases.
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II Bronchial Carcinoid
* Most patients are under 40 years of age.
* Incidence is equal for both sexes.
* There is no known relationship to cigarette smoking, or other environmental factors.
* It usually secretes hormonally active polypeptides.
* 40% of these tumors metastasize to regional nodes, and 5 to 10% metastasize to liver.
III Other (Miscellaneous) tumors
* These tumors are rare and include fibroma, fibrosarcona, leiomyoma, leiomyosarcome, lipoma,
hemoangioma, hemangiopericytoma, and chondroma.
IV Metastatic tumors of lung
* The lung is more often affected by metastatic growths.
* Both carcinomas and sarcomas arising anywhere in the body may spread to the lungs via the
blood or lymphatics, or by direct continuity.
* Usually produce discrete lesions, tend to occur in the periphery of the lung parenchyma, rather
than in the central locations of the primary bronchogenic carcinoma.
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