Lung cancer is a malignant tumour of the lungs. Most commonly it is bronchogenic carcinoma (about 90%). Lung cancer is the most lethal malignant tumour worldwide, causing up to 3 million deaths.
Exposure to carcinogens, such as those present in tobacco smoke, immediately causes small changes to the tissue lining the bronchi of the lungs (the bronchial mucous membrane). This effect is cumulative, and over time with continued exposure more and more tissue gets damaged until a tumour develops. If the tumour grows inwards it may obstruct the air passageway, causing breathing difficulties. The lungs may then collapse and infections can develop, leading to lung abscess. The patient here would start to cough up blood-stained material. However, if the tumour grows outwards in to the lung it may not even be noticed by the patient before it starts to spread to other parts of the body.
lung cancer symptoms
Early symptoms of lung cancer can be simmilar to those of later signs. Common symptoms include:
- coughing up blood
- a bad, chronic cough
- chest pains
- weight loss or loss of appetite
- shortness of breath
- a hoarse voice
Depending on the type of tumor, so-called paraneoplastic phenomena may initially attract attention to the disease. In lung cancer, this symptom may be Lambert-Eaton myasthenic syndrome (muscle weakness due to auto-antibodies), hypercalcemia and SIADH. Tumors in the top (apex) of the lung, known as Pancoast tumors, may invade the local part of the sympathetic nervous system, leading to changed sweating patterns and eye muscle problems (a combination known as Horner's syndrome), as well as muscle weakness in the hands due to invasion of the brachial plexus.
Types of lung cancer
There are two main types of lung cancer categorised by the size and appearance of the malignant cells seen by a histopathologist under a microscope: small and non-small cell lung cancer. This classification although based on simple pathomorphological criteria has very important implications for clinical management and prognosis of the disease.
Small cell lung cancer
Small cell carcinoma (also called oat cell carcinoma) is the less common form of lung cancer, making up 20% of cases. It tends to start in the larger breathing tubes and grows rapidly becoming quite large. The oncogene most commonly involved is the L-myc. The "oat" cell contains dense neurosecretory granules which give this an endocrine/paraneoplastic syndrome association.
Non-small cell lung cancer
Epidermoid carcinoma (or Squamous cell carcinoma) also starts in the larger breathing tubes but grows slower meaning that the size of these tumours varies when on diagnosis.
Adenocarcinoma (or for slower growing forms alveolar cell cancer) is a form which starts near the gas-exchanging surface of the lung. It is less closely associated with smoking.
Large cell carcinoma is a fast-growing form that grows near the surface of the lung.
Posted by Staff at May 20, 2005 4:59 AMblog comments powered by Disqus