What is Lung Cancer?

What is Lung Cancer?

Fri, 15 Dec 2023

The lungs are two large organs made of spongy tissue, which lie inside the chest under the rib cage. When we breathe in, the lungs absorb oxygen and deliver it to the bloodstream. The oxygenated blood is then pumped throughout the body by the heart. When we exhale, the lungs remove carbon dioxide, a waste gas, from the bloodstream.

Lung cancer is the uncontrolled growth of abnormal cells in the lung. Normal lung tissue is made up of cells that are programmed by nature to create lungs of a certain shape and function. Sometimes the instructions to a cell go haywire these cells then start to reproduce in an uncontrolled manner without regard for the shape and function of a lung. This leads to formation of tumors that clog up the lung and make it stop functioning as it should.

Lungs are a large sized organs, thereby Lung cancer may grow for many years without getting detected or causing suspicion. In fact, lung cancer can spread outside the lungs without causing any symptoms. Adding to the confusion, the most common symptom of lung cancer, a persistent cough, can often be mistaken for a cold or bronchitis.

What are the types of lung cancer?

Lung cancers, also known as bronchogenic carcinomas, are broadly classified into two types:

Small cell lung cancers (SCLC)

  • 20%
  • Most aggressive and rapidly growing of all lung cancers
  • SCLC are strongly related to cigarette smoking
  • SCLC spread rapidly to many sites within the body and are most often discovered after they have spread extensively.
  • Referring to a specific cell appearance often seen when examining samples of SCLC under the microscope, these cancers are sometimes called oat cell carcinomas

Non-small cell lung cancers (NSCLC).

NSCLC are the most common lung cancers, accounting for about 80% of all lung cancers. NSCLC can be divided into three main types that are named based upon the type of cells found in the tumor:

  • Adenocarcinomas are the most commonly seen type (up to 50% of NSCLC).
  • While adenocarcinomas are associated with smoking, like other lung cancers, this type is observed as well in nonsmokers who develop lung cancer. Most adenocarcinomas arise in the outer, or peripheral, areas of the lungs.
  • Squamous cell carcinomas were formerly more common than adenocarcinomas; at present, they account for about 30% of NSCLC. Also known as epidermoid carcinomas, squamous cell cancers arise most frequently in the central chest area in the bronchi.
  • Large cell carcinomas, sometimes referred to as undifferentiated carcinomas, are the least common type of NSCLC.
  • Mixtures of different types of NSCLC are also seen.
  • Other types of cancers can arise in the lung; these types are much less common than NSCLC and SCLC and together comprise only 5%-10% of lung cancers:
  • Bronchial carcinoids
    • Up to 5% of lung cancers.
    • Generally small (3 cm-4 cm or less) when diagnosed
    • Unrelated to cigarette smoking
    • Carcinoid tumors can metastasize, and a small proportion of these tumors secrete hormone-like substances that may cause specific symptoms related to the hormone being produced.
    • Carcinoids generally grow and spread more slowly than bronchogenic cancers, and many are detected early enough to be amenable to surgical resection.
  • Metastatic cancers from other primary tumors in the body are often found in the lung.
  • Tumors from anywhere in the body may spread to the lungs either through the bloodstream, through the lymphatic system, or directly from nearby organs.

More About Lung Cancer

  • Introduction
  • Causes of Lung Cancer
  • Early Symptoms of Lung Cancer
  • Lung Cancer - Diagnosis
  • Lung Cancer Surgery in Delhi, India
  • Lung Cancer Patients Care Team

Lung Cancer Incidence

Lung Cancer - World scenario

In the beginning of the century, lung cancer was considered to be rare. But now it has reached epidemic proportions. This is the leading cause of cancer death in developed countries and is rising in alarming rates in developing countries. Estimates of the worldwide incidence and mortality from 27 cancers in 2008 have been prepared for 182 countries as part of the GLOBOCAN series published by the International Agency for Research on Cancer recent. Results for 20 world regions, summarizing the global patterns for the eight most common cancers have been made in this report. Overall, an estimated 12.7 million new cancer cases and 7.6 million cancer deaths occurred in 2008, with 56% of new cancer cases and 63% of the cancer deaths occurring in the less developed regions of the world. The most commonly diagnosed cancers worldwide are lung (1.61 million, 12.7% of the total), breast (1.38 million, 10.9%) and colorectal cancers (1.23 million, 9.7%). The most common causes of cancer death are lung cancer (1.38 million, 18.2% of the total), stomach cancer (738,000 deaths, 9.7%) and liver cancer (696,000 deaths, 9.2%).

Cancer is neither rare anywhere in the world, nor mainly confined to high-resource countries. Striking differences in the patterns of cancer from region to region are observed.3 5-year survival rate for lung cancer has improved only marginally from 5% in the late 1950s to 14% by 1994. This is in contrast to the 5 years survival of 52% in other cancers.4,5

Lung cancer in India

In India, Lung cancer was initially thought to be extremely rare. As per the GLOBOCAN 2008 data Lung cancer is the 4th most common cancer in India. It is the most common cancer in men and also the most common cause of cancer-related death in India in men. Even in women the incidence is increasing and is the 9th in the list of cancers in India.