The abnormal cells can no longer do the work of normal cells and they crowd out and destroy healthy tissue. Radiation may also be used, either alone or in conjunction with surgery.
Chemotherapy is another treatment.
It too can be used alone or following surgery. Chemotherapy is always used in cases of small cell carcinoma. Lung Cancer is still the most common form of cancer in the US and prevention is still the best medicine. Most common symptom is a painless mass. Redness, scaliness of nipple or breast skin discharge.