Any of a group of malignant diseases (see cancer ) that usually start in the lymph node s or lymphoid tissue s.
The two major types, Hodgkin disease and non-Hodgkin lymphoma, each have several subtypes. Diagnosis of either type requires biopsy , usually from the lymph nodes. Non-Hodgkin lymphomas may be diffuse (widespread) or nodular (concentrated in nodules); nodular lymphomas generally develop more slowly.