Sarcomatoid carcinoma of the lung overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
Sarcomatoid carcinomas are a type of cancer that looks like a mixture of carcinoma (cancer that begins in the skin or in tissues that line or cover internal organs in the body) and sarcoma (cancer of the bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue). Sarcomatoid carcinoma are rare, aggressive, malignant cancer and can occur in different organs such as the thyroid gland, bone, skin, breast, pancreas, liver, urinary tract, and lung. Sarcomatoid carcinoma of the lung is a group of poorly differentiated non-small cell lung carcinomas. Sarcomatoid cancer of the lung is a rare type of malignancy and it comprises of only 0.3% to 1.3% of cases of all lung cancers. The pathogenesis of sarcomatoid carcinoma of the lung is characterized by a rare epithelial origin, and morphologic features suggestive of a malignant mesenchymal tumor. The EGFR gene and K-ras mutations have been associated with the development of sarcomatoid carcinoma of the lung. The prevalence of sarcomatoid carcinoma of the lung is approximately 0.4 cases per 100,000 individuals worldwide. Common risk factors in the development of sarcomatoid carcinoma of the lung are smoking, family history of lung cancer, exposure to high levels of air pollution, asbestos, radiation therapy to the chest, radon gas, occupational exposure to chemical carcinogens, and previous lung diseases. If left untreated, the majority of patients with sarcomatoid carcinoma of the lung may develop distant metastasis. Prognosis is generally poor, even worse than other non-small cell carcinoma of the lung. The 5-year survival rate for patients with sarcomatoid cancer of the lung is 28.7%.
Historical Perspective
Sarcomatoid carcinoma is a rare type of malignant tumor. The name sarcomatoid carcinoma was first described by Virchow in 1865 as a “biphasic” lesion of adenocarcinomatous or squamous cell carcinoma with spindle cell or giant cell component.
Classification
Sarcomatoid carcinoma of the lung is a rare type of non-small cell lung cancer. On the basis of histopathological features, sarcomatoid carcinoma of the lung can be classified into 5 subtypes: pleomorphic carcinoma, spindle cell carcinoma, giant cell carcinoma, carcinosarcoma, and pulmonary blastoma.
Pathophysiology
Sarcomatoid carcinomas are rare, aggressive, malignant cancer and can occur in different organs such as the thyroid gland, bone, skin, breast, pancreas, liver, urinary tract, and lung. Sarcomatoid carcinoma of the lung is a group of poorly differentiated non-small cell lung carcinomas. Sarcomatoid carcinoma is defined as a biphasic tumor with morphological characteristics of both, carcinomatous and sarcomatous components. The exact pathogenesis of sarcomatoid carcinoma of the lung is not fully understood, but the EGFR and K-ras gene mutations have been associated with the development of sarcomatoid carcinoma of the lung.
Causes
The direct cause of sarcomatoid carcinoma of the lung is DNA mutations that often result in either activation of proto-oncogenes (e.g. K-RAS) or the inactivation of tumors suppressor genes (e.g. TP53) or both. The risk of these genetic mutations may be increased following exposure to environmental components.
Differentiating sarcomatoid carcinoma of the lung from other Pulmonary Diseases
Sarcomatoid carcinoma of the lung must be differentiated from pulmonary disease causing cough, weight loss, hemoptysis, and dyspnea with the of tests such as chest X-ray, CT-scan of the chest, sputum culture and stain specific for microbes. Sarcomatoid carcinoma of the lung must be differentiated from different types of lung malignancies with the help of biopsy results and immunohistopathological staining of the biopsy specimen.
Epidemiology and Demographics
Sarcomatoid carcinoma of the lung is a rare lung malignancy with aggressive characteristics. The prevalence of sarcomatoid carcinoma of the lung is approximately 0.4 cases per 100,000 individuals worldwide. The average age of patients being diagnosed is between 65 to 75 years, male to female ratio 4:1. The 3-year and 5-year survival rates for patients with sarcomatoid cancer of lung are 35.8 and 28.7%.
Risk Factors
The most potent risk factor in the development of sarcomatoid carcinoma of the lung is tobacco smoking. Other risk factors include secondhand smoke, air pollution, family history of lung cancer, radiation therapy to the chest, radon exposure, asbestos exposure and exposure to other chemical carcinogens.
Screening
The U.S. Preventive Services Task Force (USPSTF) recommends annual screening for lung cancer by low-dose computed tomography. The screening test is recommended to the smokers who are between 55 to 80 years old and who have a history of smoke 30 pack-years or more and either continue to smoke or have quit within the past 15 years (grade B recommendation).
Natural History, Complications, and Prognosis
The majority of patients with sarcomatoid carcinoma of the lung remain are initially asymptomatic. Early clinical features include chronic cough, hemoptysis, dyspnea, weight loss and fatigue. If left untreated, patients with sarcomatoid carcinoma of the lung may develop local invasion and distant metastasis. Majority of the patients with central sarcomatoid carcinoma of the lung may develop distant metastasis to esophagus, jejunum, rectum and kidney. Sarcomatoid carcinoma of lung located in the periphery of lungs tends be diagnosed later in the advanced stages with the large size and metastasis to the pleura and chest wall. Common complications of sarcomatoid carcinoma of the lung include respiratory failure, recurrent pneumonia, and distant metastasis. Prognosis is generally poor. The 3-year and 5-year survival rates for patients with sarcomatoid cancer of lung are 35.8 and 28.7%.
Diagnosis
Diagnostic Study of Choice
The diagnostic modality of choice for sarcomatoid carcinoma of the lung is CT scan of the chest. The definitive diagnosis of sarcomatoid carcinoma of the lung is made by biopsy of the tumor.
History and Symptoms
Sarcomatoid carcinoma of the lung is a rare group of non-small cell lung cancer. The patients with sarcomatoid carcinoma of the lung commonly are current smokers or have a history of smoking. Most commonly, sarcomatoid carcinoma of the lung presents as chronic cough, hemoptysis, dyspnea, fatigue, and weight loss. There are no paraneoplastic syndromes associated with sarcomatoid carcinoma of the lung.
Physical Examination
Physical examination findings of sarcomatoid carcinoma of the lung will depend on the location of the tumor. Sarcomatoid carcinoma of the lung with central location may cause crackling sounds, focal wheezing, voice hoarseness, and tachypnea. Peripheral location can present with pleurisy findings, such as reduced chest expansion. Common physical examination of patients with sarcomatoid carcinoma of the lung include: crackling or bubbling noises and decreased/absent breath sounds.
Laboratory Findings
There are no specific laboratory findings associated with sarcomatoid carcinoma of the lung.
Electrocardiogram
There are no ECG findings associated with sarcomatoid carcinoma of the lung.
X-ray
Conventional chest radiography is the initial imaging method of choice for the diagnostic evaluation of sarcomatoid carcinoma of the lung. The initial evaluation of suspected lung cancer will depend upon the results of the chest X-ray. Further evaluation of suspected lung cancer includes enhanced CT scan of the thorax, upper abdomen, and neck. Imaging features for the evaluation of sarcomatoid carcinoma of the lung include location such as central or peripheral lesion, mass characteristics such as size, shape, and margins, the presence of cavitation, and type of adenopathy such as hilar or mediastinal.