Signs and symptoms of lymphoma may include:

• Painless swelling of lymph nodes in your neck, armpits or groin
• Persistent fatigue
• Fever
• Night sweats
• Shortness of breath
• Unexplained weight loss

Doctors aren't sure what causes lymphoma. But it begins when a disease-fighting white blood cell called a lymphocyte develops a genetic mutation. The mutation tells the cell to multiply rapidly, causing many diseased lymphocytes that continue multiplying.

The mutation also allows the cells to go on living when other cells would die. This causes too many diseased and ineffective lymphocytes in your lymph nodes and causes the lymph nodes to swell.

Factors that can increase the risk of lymphoma include:

• Your age. Some types of lymphoma are more common in young adults, while others are most often diagnosed in people over 55.
• Being male. Males are slightly more likely to develop lymphoma than are females.
• Having an impaired immune system. Lymphoma is more common in people with immune system diseases or in people who take drugs that suppress their immune system.
• Developing certain infections. Some infections are associated with an increased risk of lymphoma, including the Epstein-Barr virus and Helicobacter pylori infection.