Which of the following features cannot be used to differentiate between Hodgkin's and Non Hodgkin's Lymphoma ?
Extranodal involvement
Spread contiguity
Painless lymphadenopathy
Localisation to a particular group of lymph nodes
Hodgkin lymphoma, like NHL, usually manifests as painless lymphadenopathy.  Although a definitive distinction from NHL can be made only by examination of a tissue biopsy,  several clinical features favor the diagnosis of Hodgkin lymphoma. After the diagnosis is established, staging is used to guide therapy and determine prognosis.