Lung Carcinoma: Types and Characteristics

Lung Carcinoma: An In-depth Analysis

• Lung carcinoma is also known as bronchogenic carcinoma
• Bronchogenic carcinoma is a malignant neoplasm originating in the airways or lung parenchyma
• Malignant tumors are cancerous, grow aggressively, and metastasize
• Benign tumors are non-cancerous, grow non-aggressively, and do not metastasize; they do not invade surrounding tissues.

Types of Lung Carcinoma

• Non-small cell lung carcinoma (NSCLC):

  • Adenocarcinoma (approximately 40%): Common, including bronchioloalveolar carcinoma (BAC).
  • Squamous cell carcinoma (approximately 25-30%): Often arises in mucous membrane of proximal bronchi.
  • Large cell undifferentiated carcinoma (approximately 10-15%): Rare, large, rapidly-growing tumors often located in peripheral lung tissue.

• Small cell lung carcinoma (SCLC):

  • Accounts for approximately 10-15% of lung cancers
  • Characterized by early and widespread metastasis.
  • Mostly found in heavy smokers.

History

• Significant advancements have been made in understanding and treating lung cancer over the years.
• Many treatments, such as chemotherapy and targeted therapy, have greatly impacted survival rates.

Epidemiology

• Lung cancer accounts for 1.37 million deaths worldwide annually.
• In the US, it's the leading cause of cancer mortality.
• Risk factors include smoking (most common), environmental exposures, and occupational exposures.
• Lung cancer is typically diagnosed at later stages, often when it has already advanced.
• Lung cancer is the leading cause of cancer death for most ethnic groups.
• Approximately 234,580 Americans are estimated to be diagnosed with this condition every year.

Pathophysiology

• Lung cancer arises in the bronchial tree in different locations.
• Lung tumors are heterogeneous, meaning they exhibit variations in their characteristics and behaviors.
• There are two significant types of lung cancer: NSCLC and SCLC. Each type presents with different patterns of growth and spreads.

Etiology- NSCLC

• 90% of NSCLC is caused by tobacco smoke exposure
• Occupational and environmental factors contribute, including air pollution, radon exposure, asbestos, nickel, chromium, silica, chloromethyl ethers and beryllium exposure.
• Genetic factors can also play a role in the development of NSCLC.

Etiology- SCLC

• Mostly caused by tobacco use
• Occupational exposures such as radon (high levels) and chloromethyl ether exposure can increase the risk of SCLC.

Clinical Signs and Symptoms

• NSCLC: Often asymptomatic until advanced, with symptoms like cough (persistent and worsening), hemoptysis, dyspnea, chest pain, hoarseness, loss of appetite, and wheezing.
• SCLC: Mostly symptomatic at presentation; common symptoms are bone pain, persistent cough, fatigue, weakness, dyspnea, wheezing, hoarseness, and loss of appetite.

Regional Spread Complications

• NSCLC and SCLC can cause regional spread complications, including airway/esophageal compression, Horner's syndrome, Pancoast syndrome, phrenic nerve palsy, recurrent laryngeal nerve palsy, and SVC syndrome.
• SCLC can lead to laryngeal invasion, leading to vocal chord paralysis, phrenic nerve compression, dysphagia (swallowing difficulty), superior vena cava syndrome, pericardial effusion/tamponade, cervical/supraclavicular lymph node enlargement.

NSLC Assessment & Diagnosis

• Imaging techniques like CT scans (without contrast), MRI, and PET scans are used to visualize the extent of the cancer
• Biopsy methods are available to obtain tissue samples for histologic examination. Confirmation can be done from sputum studies, bronchoscopy, mediastinoscopy and/or thoracoscopy (video-assisted).

SCLC Assessment & Diagnosis

• Imaging methods such as chest X-rays, CT scans without contrast, MRI are used
• Assessment and diagnosis of SCLC may also include CT scan without contrast, MRI, and/or MRI if brain metastasis is suspected.

Stages of Lung Cancer

• Staging systems are used to determine the extent of the cancer (i.e., size, presence of lymph node involvement, and metastasis).
• Lung cancer is often categorized into four stages (I-IV), with stage IV being the most advanced stage, signifying widespread disease.

Treatment

• Chemotherapy can kill cancerous cells and stop further cancerous cell division, but it can also harm healthy cells.
• Targeted therapy minimizes harm to normal cells while targeting cancerous cells.
• Surgery is a treatment option for removing tumors.
• Radiation therapy is a cancer treatment that uses high-energy x-rays or other radiation types to kill cancer cells. External and internal radiation are two types used.
• Immunotherapy strengthens the body's immune system to fight cancer.

Prevention

• Smoking cessation is crucial to reduce the risk
• Minimizing exposure to carcinogens (like asbestos and radon) is essential
• Regular screening for early detection is beneficial

Prognosis

• Results vary based on the stage of lung cancer and type of treatment received.
• NSCLC; Distal metastasis results in a 4.5% survival rate; localized NSCLC has a 55.6% survival rate.
• SCLC; Extensive-stage has a survival rate of about <10 months; limited stage survival rate is about 80%
• Mechanical ventilation can be a life-saving measure but carries poor prognoses when used to treat respiratory failure.

Resources and Additional Information

• Numerous sources (including medical journals, websites, and books) are available for detailed study of lung carcinoma.