Extranodal manifestations of lymphoma

•. Extranodal manifestations of lymphoma are much commoner in non‐Hodgkin's lymphoma (NHL) than in Hodgkin's disease (HD) and, with the increasing frequency of NHL, will be seen more often. •. At presentation, lung involvement is seen more frequently in HD (12%) than in NHL (4⇒) and is almost always associated with mediastinal or hilar adenopathy. •. The sensitivity of cross‐sectional imaging for the detection of splenic involvement remains low, as involvement is usually diffuse. •. The gastrointestinal tract is the commonest site of primary extranodal lymphoma and gastric involvement accounts for about 80% of all gastrointestinal lymphoma in adults. •. Genitourinary lymphoma is usually only seen in advanced disease, seldom at presentation. The testicles are the most common organ to be involved. •. Bone marrow involvement is present in a minority of patients with HD but in 20–40% of patients with NHL. MRI is the most sensitive imaging method of detecting involvement. •. Primary central nervous system lymphoma accounts for up to 30% of cases of NHL and is restricted almost entirely to the brain.