Atlas of pathophysiology, 2 Edition

Part II - Disorders

Respiratory Disorders

Lung Cancer

Lung cancer is the leading cause of cancer death among men and women.

Age Alert

Lung cancer is fairly rare in people younger than age 40. The average age at diagnosis is 60.

The two main types of lung cancer are small-cell lung cancer (SCLC) and non–small-cell lung cancer (NSCLC). If the cancer has features of both, it's called mixed small-cell/large-cell cancer.

About 20% of all lung cancers are SCLC. Although the cancer cells are small, they can multiply quickly and form large tumors that spread to the lymph nodes and to other organs, such as the brain, liver, and bones. Therefore, treatment must include drugs that kill this widespread disease. SCLC is extremely rare in someone who has never smoked.

The remaining 80% of lung cancers are NSCLC, which includes three subtypes. The cells in these subtypes differ in size, shape, and chemical makeup. They include:

·   squamous cell carcinoma, which is commonly linked to a history of smoking and tends to be found centrally, near a bronchus

·   adenocarcinoma, which is usually found in the outer region of the lung

·   large-cell undifferentiated carcinoma, which can appear in any part of the lung and tends to grow and spread quickly. (This type of cancer has a poor prognosis.)

Causes

·   Tobacco smoke

·   Carcinogenic industrial and air pollutants (asbestos, uranium, arsenic, nickel, iron oxides, chromium, radioactive dust, coal dust, radon)

·   Familial susceptibility

Pathophysiology

Lung cancer begins with the transformation of one epithelial cell of the airway. The bronchi, and certain portions of the bronchi, such as the segmental bifurcations and sites of mucus production, are thought to be more vulnerable to injury from carcinogens.

As a lung tumor grows, it can partially or completely obstruct the airway, resulting in lobar collapse distal to the tumor. A lung tumor can also hemorrhage, causing hemoptysis. Early metastasis may occur to other thoracic structures, such as hilar lymph nodes or the mediastinum. Distant metastasis can occur to the brain, liver, bone, and adrenal glands.

Signs and symptoms

·   Cough, hoarseness, wheezing, dyspnea, hemoptysis, and chest pain

·   Fever, weight loss, weakness, and anorexia

·   Bone and joint pain

·   Cushing's syndrome

·   Hypercalcemia

·   Hemoptysis, atelectasis, pneumonitis, and dyspnea

·   Shoulder pain and unilateral paralysis of diaphragm

·   Dysphagia

·   Jugular vein distention and facial, neck, and chest edema

·   Piercing chest pain, increasing dyspnea, and severe arm pain

Diagnostic test results

·   Chest X-ray shows an advanced lesion, including size and location.

·   Sputum cytology reveals possible cell type.

·   Computed tomography (CT) scan of the chest delineates tumor size and relationship to surrounding structures.

·   Bronchoscopy locates tumor; washings reveal malignant cell type.

·   Needle lung biopsy confirms cell type.

·   Mediastinal and supraclavicular node biopsies reveal possible metastasis.

·   Thoracentesis shows malignant cells in pleural fluid.

·   Bone scan, bone marrow biopsy, and CT scan of the brain and abdomen reveal metastasis.

Treatment

·   Lobectomy, wedge resection, or pneumonectomy

·   Video-assisted chest surgery

·   Laser surgery

·   Radiation

·   Chemotherapy

P.97

TUMOR INFILTRATION IN LUNG CANCER

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