Benign tumours are covered by a fibrous outer capsule. They normally remain confined to their original location and do not spread to other parts of the body and cause little damage. The sloughed off cells of malignant tumours reach distant sites through blood, and wherever they get lodged in the body, they start a new tumour there. This property called metastasis is the most feared property of malignant tumours.
Cocaine interferes with the transport of dopamine.
Anti-retroviral drugs are only partially effective. They can only prolong the life of the patient but cannot cure AIDS completely.
Mucosa-associated Lymphoid Tissue (MALT) is a secondary lymphoid tissue.