When malignant cells start developing in the lungs, it is termed as lung cancer It is a significant cause of death in both the genders in the United States and claims more lives than prostate, colon, breast, and ovarian cancers combined. The initial symptoms include persisting cough, chest pain, hoarseness in voice, shortness of breath, loss of weight, and bone pain.

Causes of lung cancer

• Smoking tobacco
  According to the Centers for Disease Control and Prevention (CDC), 90 percent of the cases of lung cancer occur due to incessant cigarette smoking. Studies reveal that tobacco contains about 7000 carcinogens including nitrogen oxide and carbon monoxide. Smoking initiates a change in the lung tissue which may ultimately lead to cancer.
• Genetics
  If any immediate blood relative, including parents, siblings, grandparents, uncle or aunts has suffered from lung cancer, then chances of contracting the disease increase manifold. Even if the individual does not smoke, he or she remains susceptible to this disease.
• Age
  The American Cancer Society reveals that the chances of suffering from lung cancer increase with the age of patients. Every two out of three individuals diagnosed with lung cancer are above 65 years of age.
• History of lung diseases
  Occurrences of severe lung diseases in the past including chronic obstructive pulmonary disease (COPD), tuberculosis, chronic bronchitis, and emphysema also increase the risk of lung cancer.
• Secondhand smoke
  CDC states that approximately 3000 individuals die every year from lung cancer ,  among those who have never smoked in their life. In these cases, exposure to passive smoking at home and other public places is the main culprit. The government is taking initiatives to prevent people from smoking in public areas.
•   Environmental factors
  Exposure to certain materials including radon, asbestos, arsenic, beryllium, cadmium, vinyl chloride, mustard gas, chromium compounds, coal products, and chloromethyl ethers increases the chances of developing lung cancer. According to the CDC, exposure to radon is the second major cause of the disease.

  Types of lung cancer
There are different types of lung cancer based on the macroscopic appearance of the malignant cells.

• Small  Cell Lung Cancer (SCLC)
  It is the most aggressive and rapidly developing type of lung cancer, and about 10 to 15 percent of the patients suffer from it. Studies have revealed that cigarette smoking is strongly related to the occurrence of SCLC. This form of the disease rapidly spreads to other organs (metastasize), and in most of the cases, the diagnosis takes place when the malignancy is already in the advanced stages.
• Non-small Cell Lung Cancer (NSCLC)
  It is an umbrella term used to signify different types of lung cancer behaving similarly including adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. In 85 percent of the cases, the patient suffers from NSCLC.

  In addition to the above types, there are some less common types of lung cancer like bronchial carcinoids. Though lung cancer is a severe disease, early detection and rapid initiation of treatment can improve the life expectancy considerably.