Reed sternberg cells are found in-

Hodgkin&;s lymphoma is characterised by the presence of neoplastic giant cells called Reed Sternberg cells.These cells release factors that induce the accumulation of reactive lymphocytes, macrophages, and granulocytes, which typically make up greater than 90% of tumour cellularity. RS cells are derived from the germinal centre or post germinal centre B cells. Reference : Robbins and Cotran Pathologic basis of disease.South Asia Edition volume 1.page no. 607