Understand Lung Cancer

Lung cancer is the uncontrolled growth of malignant cells in lung tissue. Cancers that develop in the lung can arise from bronchial cell: these are lung cancers themselves (or primitive) to start bronchial and it is called lung cancer.


Lung cancer is the leading cause of cancer deaths in both men and women. The causal link between cigarettes and lung cancer is now established, not only epidemiologically, but also through identification of carcinogens in tobacco smoke and analysis of the effect of these carcinogens on specific oncogenes expressed in lung cancer.


It is estimated that cigarette smoking causes 85% to 90% of cases of lung cancer. The number of deaths resulting from lung cancer has been decreasing in men, and appears to be leveling off in women after increasing for several decades. Environmental risk factors for the development of lung cancer include exposure to environmental tobacco smoke, radon gas, asbestos, metals (arsenic, chromium, nickel, iron oxide), and industrial carcinogens.


The World Health Organization (WHO) distinguishes between two forms of lung cancer, is ti Lung cancer or bronchogenic cancer non-small cell and small cell lung cancer. Both types of tumors grow, propagate differently in the body and can not be treated in the same way:


Small cell lung cancer

Small cell lung carcinoma (SCLC) whitch accounts for 13% to 15% of cases is often widespread at the time of diagnosis, so that treatment is limited to chemotherapy and/or radiation therapy. Some studies suggest that 60% to 70% of patients with SCLC have evidence of distant spread at the time of initial diagnosis. It is rarely amenable to surgical resection and has a very aggressive course.



Though NSCLC is staged using the TNM international system, SCLC is not because micrometastases are assumed to be present on diagnosis.


SCLC is divided into two categories:


  • Limited disease (30%), when the tumor is limited to the unilateral hemithorax (including contralateral mediastinal nodes)
  • Extensive disease (70%), when the tumor extends beyond the hemithorax (including pleural effusion)


This is a very specific form since at the time of diagnosis, the risk that the cancer has already dispersed elsewhere in the body is high. It is almost never treated with surgery. Instead, there are chemotherapy and radiotherapy can be used instead.



Non-small cell lung cancer

Three histologic categories comprise NSCLC; these spread more slowly. They may be cured in the early stages following resection, and they respond similarly to chemotherapy. NSCLC is much more common than SCLC, and accounts for about 80% to 90% of all lung cancer cases. Types of NSCLC include:2


  • Adenocarcinoma (40% of cases) arises from mucus glands originating in any epithelial cell within or distal to the terminal bronchioles.
  • Squamous cell carcinoma (25%–35% of cases) arises from the bronchial epithelium, and is typically centrally located. Squamous cell carcinoma tends to have a better prognosis than the other two types because it is slower growing and can take several years to progress from a confined tumor into invasive cancer.
  • Large cell carcinoma (10%–15% of cases) is a heterogeneous group of relatively undifferentiated tumors that share large cells and do not fit into other categories. Large cell carcinomas typically have rapid doubling times and an aggressive clinical course.



NSCLC staging

For NSCLC, the TNM international staging system is used: T describes the size and location of the primary tumor, N describes the presence and location of nodal metastases, and M refers to the presence or absence of distant metastases. More details are provided in the table below:







Tumor (T)


Positive malignant cytology results, no lesion seen


Diameter smaller than or equal to 3 cm


Diameter larger than 3 cm


Extension to pleura, chest wall, diaphragm, pericardium, within 2 cm of carina, or total atelectasis


Invasion of mediastinal organs (eg, esophagus, trachea, great vessels, heart), malignant pleural effusion, or satellite nodules within the primary lobe

Regional lymph node involvement (N)


No lymph nodes involved


Ipsilateral bronchopulmonary or hilar nodes involved


Ipsilateral mediastinal or subcarinal nodes


Contralateral mediastinal, hilar, any supraclavicular nodes involved

Metastatic involvement (M)


No metastases


Metastases present