Squamous Cell Carcinoma of the Lung

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The lungs essentially provide the interface between air and blood. The
lungs consist of a series of folded membranes (the alveoli), which are
located at the ends of very fine branching air passages (bronchioles).

The lungs are passive elastic organs which are expanded when the chest
wall expands. The negative pressure created by expansion of the chest
sucks in air through the air passages.

Air is drawn in through the nose and mouth and down through the trachea
(windpipe). The trachea divides into a right main bronchus and left main
bronchus to supply each lung. The left lung is divided into a left upper
lobe and left lower lobe with the middle section of the lung being
referred to as the lingula. The right main bronchus splits into 3 to
supply the right upper lobe, right middle lobe and right lower lobe. The
bronchi then divide into smaller bronchioles which ultimately terminate in

the alveoli.

Blood which arrives into the lungs from the pulmonary artery enters
smaller and smaller blood vessels until it ends up in the capillaries
located within the walls of the alveoli. In this moist environment, oxygen

diffuses from the air within the alveoli, through the alveolar membrane
into the blood stream. Carbon dioxide moves out of the blood stream into
the air within the alveoli and when the lungs contract the carbon dioxide
is expelled out of the air passages.

There are a number of cells from which tumours may arise from different
parts within the lung system

Incidence:

It is common and occurs with increasing age. Sex incidence is more common
in males, but in recent years the incidence of the disease in females is
rapidly increasing. This is mainly due to increased smoking habits in
females.

Geographically, the tumour is found worldwide, but it is especially common

in countries with a high tobacco consumption.

Predisposing Factors:

Cigarette smoking is the main predisposing factor. In recent years, it has

been recognised that passive smoking (eg. from a first degree relative in
a house of smokers) can also put people at risk. Generally, the risk
increases with the number of cigarettes smoked.

Exposure to asbestos increases the risk of developing this tumour. The
combination of asbestos exposure plus cigarette smoking is particularly
harmful.

Radiation exposure damages the DNA material within the cells and can also
cause lung cancer.

Radon (a radioactive gas) exposure from our normal surrounding
environment, if higher than normal, can predispose to lung cancer. This
evidence is mainly based upon population studies which show that people
living in areas with a high radon content are prone to increased
incidences of a variety of cancers.


Macroscopic Features:

Squamous Cell Carcinoma of the Lung appear as a lump found within the
bronchi or bronchioles. It can be seen to be invading adjacent tissue and
may be haemorrhagic or necrotic.

Natural History:

This type of tumour spreads by the lymphatic vessel to lymph nodes located

within the lung, mediastinum and thorax. If spread by the blood stream, it

can lead to deposits of tumour in the liver, the opposite lung, bone and
brain.

Prognosis:

The prognosis is best for early tumours, usually asymptomatic ones which
are found incidentally on a chest x-ray. These early tumours can be
removed surgically and have a reasonable chance of cure. Cure of early
tumours found in this way, which are less than 2cm in diameter, may
approach 30%. Similar tumours treated by radiotherapy because of patient
choice or certain anatomical considerations may achieve a 20% cure with
radiotherapy alone. The tumour doubles in size approximately every 2
months and a number of these tumours can be quite aggressive.

Approximately 50% of patients with this tumour will survive 1 year
although only 1 in 8 will survive 5 years.

Clinical History:

Symptoms for this illness are coughing, shortness of breath, haemoptysis
(coughing blood), weight loss, lethargy and alteration in the amount of
sputum produced. Occasionally, with peripheral tumours which involve the
chest wall or with larger tumours situated centrally, a patient can
present with pain. If it involves the chest wall this is usually somatic
pain, whereas if it is a large tumour which is involving the central
portion of the lung this will be of the visceral pain type.
Clinical Examination:

Examination of the patient may show abnormal expansion on the side
affected by the tumour due to obstruction of the bronchus. A pleural
effusion may be present which indicates a poorer prognosis.
Lymphadenopathy may be palpable, especially in the supraclavicular region.

If the disease has spread to the liver, the liver may well be enlarged and

irregular. A reasonable number of patients present with brain metastases
and sometimes a seizure (fit) or focal neuro

Improvement in symptoms is an important measurement. Specific monitoring
may be done through a chest x-ray to watch for recurrence of the disease.
CT scans and, in more recent years, PET have been useful to monitor
disease
recurrence or response to treatment.

The symptoms that may require attention are shortness of breath from
pleural effusion, lymphangitis and destruction of normal lung tissue.

Coughing may be a feature from irritation of the bronchioles or bronchus
by tumour tissue.

Metastases may cause pain, either from the liver (visceral pain) or from
the bone (somatic pain).

Careful monitoring should take place, looking for spinal cord compression
which may complicate vertebral metastases.