Both Hodgkin's lymphoma (formerly known as Hodgkin's disease) and non-Hodgkin's lymphoma are lymphomas, a type of cancer that begins in a subset of white blood cells called lymphocytes. Lymphocytes are an important part of your immune system. The main difference between Hodgkin's and non-Hodgkin's lymphoma is in the specific lymphocyte each involves.
A doctor can tell the difference between Hodgkin's and non-Hodgkin's lymphoma by examining the cancer cells under a microscope. If in examining the cells, the doctor detects the presence of a specific type of abnormal cell called a Reed-Sternberg cell, the lymphoma is classified as Hodgkin's. If the Reed-Sternberg cell is not present, the lymphoma is classified as non-Hodgkin's.
The distinction is important because the treatment and outcomes for each type can be very different.