Cancer

Healthy cells respond to growth signals, repair genetic injury, stop dividing when appropriate, and undergo programmed cell death when they can no longer function safely. Cancer begins when accumulated genetic or epigenetic changes allow a cell clone to bypass these controls. The abnormal cells continue to divide, resist cell death, recruit a blood supply, and alter the surrounding tissue. A malignant tumour can then invade nearby structures and enter lymphatic or blood vessels to establish disease at distant sites. That biology produces two different groups of clinical findings. Local growth may cause a mass, obstruction, pain, bleeding, impaired organ function, or compression of nerves and vessels. Systemic effects may include fatigue, anorexia, weight loss, fever, or night sweats. Inflammation and increased metabolic demand contribute to cancer-related wasting; the symptom is not simply “tiredness.” The blood and immune systems are affected by both the malignancy and its treatment. Marrow infiltration or myelosuppressive therapy can reduce red cells, platelets, and neutrophils: - Reduced red-cell production or blood loss can produce anaemia, fatigue, dizziness, dyspnea, or tachycardia. - Thrombocytopenia increases the risk of...