Lung cancer Flashcards
What is the peak incidence in age of Lung cancer?
Lung cancer is the second most common cancer in the UK with a peak incidence in the 50-60yo age group. It is the most common cause of cancer death in both men and women - this is because of its poor prognosis (less than 10% of patients remain alive 5 years from diagnosis).
Cause of lung cancer?
80-90% of cases of lung carcinoma can be attributed to cigarette smoking. Cigarette smoke contains a large number of carcinogenic compounds eg. benzopyrene.
But, since lung cancer develops in only about 10% of heavy smokers and about 10-20% of lung cancers occur in non-smokers, other factors must predispose to its development, for example:
• industrial hazards eg. asbestos, arsenic, chromium, radiation.
• environmental exposure eg. radon gas (Cornwall).
• genetic factors eg. EGFR (epidermal growth factor receptor) gene mutations (more common in non-smokers)
Pathology of lung cancer?
The majority of lung cancers are carcinomas. They can be subdivided into four main groups and a miscellaneous category:
• squamous cell carcinoma (25%)
• adenocarcinoma (40%)
• small cell carcinoma (15%)
• large cell carcinoma
• others (eg. carcinoid, large cell neuroendocrine carcinoma etc)
What is the most common site of metastatic cancer?
Lungs
Squamous cell carcinoma of the lungs
• shows a strong association with smoking.
• tends to arise in the larger airways near the hilum.
• graded as well, moderately or poorly differentiated.
• a well-defined ‘metaplasia-dysplasia-carcinoma’ sequence leads to its development:
Columnar (glandular) + smoking = metaplasia –> squamous –> dysplasia ad carcinoma in situ
Adenocarcinoma of the lungs
- Increasing in incidence (the reason for this isnt entirely clear)
- The most common type of cancer in non-smokers, where it may be associated with mutations in the EGFR gene.
- Tends to arise in the peripheral smaller airways
- Graded as well, moderately and poorly differentiated
- Precursor (premalignant) lesion is called atypical adenomatous hyperplasia (equivalent to dysplasia). It is asymptomatic
Small cell carcinoma of the lungs
• Shows the strongest association with smoking
• Usually arise in a central location
• Highly aggressive tumour, notorious for its rapid rate of growth and early spread
• Not graded (by definition, small cell carcinoma is high grade)
No recognition precursor (premalignant) lesion
Large cell carcinoma of the lung
Undifferentiated carcinomas that cannot be otherwise categorised microscopically i.e. they lack the morphological features of other form of lung cancer.
Tissue diagnosis of lung cancer
Central lesions: (ie. near the hilum) are suited to sampling at bronchoscopy:
• biopsy (histology) and/or washings, brushings (cytology)
Peripheral lesions are more suited to CT-guided sampling:
• biopsy (histology) and/or FNA (cytology)
Staging of lung cancer
Both small cell and non-small cell carcinoma are staged using the TNM system.
Imaging has a very important role in staging lung cancer:
• CT is good for T (tumour) staging. It is less sensitive for the detection of involved lymph nodes and distant
metastases.
• PET or PET-CT enables more accurate staging of N (nodes) and M (metastases) prior to surgery.
Clinical presentation of lung cancer
Local symptoms and signs
• cough (involvement of central airways) - the most common initial presenting symptom.
• haemoptysis (bleeding from tumour).
• stridor/wheeze (large airway obstruction).
• hoarse voice (invasion of left recurrent laryngeal nerve).
• breathlessness (large airway obstruction and/or development of associated pleural effusion).
• chest wall pain (chest wall involvement).
• non-resolving pneumonia (tumours may partially obstruct airways leading to infection).
SVC obstruction
The superior vena cava (SVC) is the major drainage vessel for venous blood from SVC obstruction the head, neck, upper extremities, and upper thorax. It is a thin-walled, low-
pressure, vascular structure located in the mediastinum and surrounded by
relatively rigid structures such as the sternum, trachea and aorta.
Obstruction of the SVC is usually due to extrinsic pressure of a tumour and most commonly the tumour is a right sided lung cancer (omen small cell carcinoma). [Less commonly, compression is caused by mediastinal lymphadenopathy due to metastatic carcinoma or involvement by lymphoma].
The subsequent obstruction to flow causes an increased venous pressure, which results in interstitial oedema and retrograde collateral flow. The collateral venous return to the heart from the upper half of the body is through the azygous venous system, internal mammary venous system and long thoracic venous system. Despite these collateral pathways, venous pressure is almost always elevated.
The most common symptom of SVC obstruction is shortness of breath. Other
symptoms include facial swelling, head fullness, cough, arm swelling, chest pain, dysphagia, hoarseness, stridor.
SVC obstruction is an oncological emergency because it may lead to life-threatening complications such as laryngeal oedema, cerebral oedema or decreased cardiac output.
Pancoast’s tumour
Pancoast’s tumour is a cancer in the apex of the lung which involves the 8th cervical and 1st and 2nd thoracic nerves. It may manifest as Pancoast’s syndrome (shoulder pain radiating in an ulnar distribution down the arm) or Horner’s syndrome.
Horner’s syndrome
Horner’s syndrome is characterised by: • endophthalmos (eyeball depression). • ptosis (droop) of upper eyelid. • miosis (pupil constriction). • anhidrosis (absence of sweating). There are many causes of Horner’s syndrome, of which Pancoast’s tumour is one. It is due to sympathetic nerve infiltration by tumour, particularly T1.
Systemic symptoms of lung cancer
Systemic symptoms refer to the general effects of the tumour mass on the body, giving rise to non-specific constitutional symptoms eg. weight loss, lethargy, vague sense of ill health.
