There are two categories:

1. Hodgkin's disease characterized by Reed-Sternberg cells and cure rates of up to 85%.

2. Non-Hodgkin's lymphoma (NHL) are further divided into low, intermediate or high grade depending on histological appearances. Paradoxically, low grade disease has the longest survival from diagnosis. They survive 10 to 12 years, but the disease is proven incurable. High grade disease demands aggressive chemotherapy, with cure rates up to 75%, but the treatment is poorly tolerated by older patients. The Revised European American Lymphoma (REAL) classification essentially describes all the recognized distinct clinical entities, but significantly groups all the low grade NHL into one group.

The Cotswolds meeting of 1982 resulted in a widely adopted staging system for lymphomas. The  powerful prognostic significance of constitutional symptoms was reflected in all patients being classified as A or B, that is, with or without systemic symptoms regardless of the anatomical spread of the disease (stages 1 to 4) For formal purposes, only three B symptoms are acceptable:

1. unexplained weight loss of more than 10% within six months

2. documented fevers >38.5 degree C (Pel-Ebstein) on two separate occasions.

3. drenching night sweats necessitating changing the pajamas or bed clothes.

These symptoms are very characteristic  and often the higher the grade of lymphoma, the more accurately the patient can recall their onset. Burkitt's lymphoma is probably the fastest growing lymphoma and the history is classically as short as six weeks. More typically, the onset is insidious and it is the spouse who has detected the changes. These B symptoms are due to cytokine release either from the tumour cells or recruited normal lymphocytes. The principal agents incriminated are Tumour Necrosis Factor and Interluekin-1. 20% of cases of Hodgkin's disease have a peripheral blood and marrow eosinophilia secondary to high levels of interleukin-5.