Lung Cancer - An Overview

 Lungs are two viral spongy organs (on both sides of our chest) facilitating oxygen inhale and carbon dioxide exhale. But as per current statistics WHO points out lung cancer as a leading cause of death globally. Use of tobacco, particularly smoking is accounted as the prime cause of lung cancer. India possesses second rank in tobacco consumption and third rank in its production, so spreading awareness of the frightening outcome of this habit is most important.

Anatomy and physiology of normal lungs

Healthy lungs are protected by our rib cage along with the heart. We have two lungs, on either side of our chest. The right lung is much larger and contains three lobes while the left lung is smaller with only two lobes as it shares the space with the heart.

The inhaled air passes through the windpipe called the trachea, which is divided into two bronchi, each providing oxygen to respective lungs (the left bronchi supply oxygen to the left lung, and the right bronchi supply to the right lung). Both bronchi are further divided into many bronchioles, each reaching to air sacs called alveoli. Alveoli are balloon-like sacs that inflate while inhale and deflate while exhale. From alveoli oxygen passes to blood and through blood reaches every part of the body.

Lungs have a thin outer lining called pleura, which helps the lungs to slide back and forth during inhale and exhale. The lower part of the lungs is protected by a muscular dome called the diaphragm. It provides up-and-down movement as we breathe in and out.



Lung cancer

Cancer develops in the lung tissues, commonly in the cells of the trachea, bronchi, and bronchioles. Lung cancer can be of two types.

1.  Small cell lung cancer (SCLC) is named based on the nature of cancer cells under a microscope. This is a rapidly proliferating type of cancer that accounts for around 15% of the total lung cancer cases. It is strongly associated with a long-term history of tobacco smoking. Based on the growth and proliferation of cancerous cells, there are two types of small-cell lung cancers:

a) Small cell carcinoma (Oat cell cancer) is a common type of SCLC, which grows and spreads to other body parts even in the early stages of the disease.

b)  Combined small cell carcinoma was found to contain both small and non-small cells, so named combined small cell carcinoma. It is a comparatively uncommon type of lung cancer.

2.  Non-small cell lung cancer (NSCLC) accounts for the remaining 85% of lung cancer cases. Further divided into three:

a)    Adenocarcinoma – The most common type of lung cancer type. This is commonly found in non-smokers and those who have previous smoking habits. Both primary and secondary smoking can induce adenocarcinoma. It usually develops on the exterior layers of the lungs.

b)  Squamous cell carcinoma – the second largest type of lung cancer and mostly caused by smoking. This is the most common type of lung cancer caused by smoking. It usually occurs in the middle layer of the lungs and bronchi where squamous cell lining is present.

c)  Large cell carcinoma – A rare type of lung cancer among the group. WHO categorizes undifferentiated non-small cell carcinomas under large cell carcinoma. The microscopic examination shows that the cancer cells are pretty large with round or irregularly shaped nuclei, the chromatin network and nucleoli are present.


Causes of lung cancer


       
         Symptoms of Lung cancer


Spreading of lung cancer 

·       Through tissue – the cancer cells grow and spread to the neighbouring tissues and organs.

·   Through lymph – the cancer cells may shed into the lymph from its origin, travel through lymphatic fluids, and start to grow at a distant location within the body.

·       Through blood – the shed cancer cells can fall into the blood flow and spread to a distant organ.




Diagnostic methods for lung cancer

·   Chest X-ray – Primary evaluation test to diagnose any lung ailments. If something is found abnormal, proceed to further tests to confirm.

·    CT scan – Computed Tomography scan captures detailed cross-sectional images of the lungs.

·  PET scan – The patient is injected with a radioactive dye, which emphasizes the tumour or disease area for detailed evaluation.

·   MRI scan – The detailed images of the tumour area are captured using magnetic resonance technology.

·     Sputum cytology – A laboratory test for the diagnosis of cancer cells in sputum.

· Thoracentesis – A needle aspiration of fluid accumulated around the lungs. Fluid accumulation is an abnormal condition that should be evaluated in a laboratory.

·     Endobronchial ultrasound – A bronchoscope (a camera and an aspiration needle attached to a flexible tube) is inserted via mouth or nose into the lungs of the patient to get a close look at the tumour in the lungs. It also collects a biopsy sample of the abnormal tissue for microscopic evaluation.

·     Fine needle aspiration biopsy – The abnormal tissue or tumour tissue is collected for biopsy examination using a fine needle which is inserted into the lungs. It is performed with the help of a special computer-based scanning to locate the abnormal tissue.




Treatment methods for lung cancer


 
Prevention of lung cancer


References

1.   Dela Cruz CS, Tanoue LT, Matthay RA. Lung cancer: epidemiology, etiology, and prevention. Clin Chest Med. 2011 Dec;32(4):605-44. doi: 10.1016/j.ccm.2011.09.001. PMID: 22054876; PMCID: PMC3864624.

2.     Myers DJ, Wallen JM. Lung Adenocarcinoma. [Updated 2023 Jun 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519578/

3.   Sabbula BR, Gasalberti DP, Mukkamalla SKR, et al. Squamous Cell Lung Cancer. [Updated 2024 Feb 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK564510/

4.   Fan Z, Schraeder R. The Changing Pathology of Lung Cancer. Surgical Oncology Clinics of North America, 2011;20(4):637-653. 10.1016/J.SOC.2011.07.004.

5.  Basumallik N, Agarwal M. Small Cell Lung Cancer. [Updated 2023 Jul 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482458/

6.     https://www.cancer.gov/types/lung/patient/non-small-cell-lung-treatment-pdq


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