It is a cancer, i.e. an abnormal cell growth forming a tumour, which develops within the lymphatic system.
The lymphatic system contains a network of vessels, or thin tubes, connecting certain organs called lymph nodes. We can find them particularly in the armpit, groins, neck, thorax and abdomen and they can sometimes be felt when they are inflamed by an infection.
The lymphatic system carries whitish liquid called lymph, which contains lymphocytes. These are white blood cells, which have an important role in infection control since the immune system, of which it is part, is responsible for the defence of the body against external aggressions.
The lymphoma is a tumour caused by the abnormal growth of lymphocytes and it can appear in a lymph node or in another location.