In this chapter, at first the short functional antomy of lymphoreticular system is described. Inflammation of lymphnodes, specific and non-specific lymphadenitis, reactive changes of the lymphnode and lymphangitis, their etiological factors, gross and microscopic features are described. Also, the malignant tumors of lymphnode, Hodgkin and non-Hodgkin lymphoma, their etiopathogenesis, classification, gross and microscopic features and diagnostic modalities are described. Different immunohistochemical markers for lymphoreticular malignancy are also mentioned.